Bozok RAT

What is Bozok?

Bozok is a Remote Access (Administration) Trojan, or simply a RAT. Malware of this type allows cyber criminals responsible to monitor and control victims' computers. Bozok can be used to upload and download files to/from the victim's computer, start and end processes, modify the registry, steal stored (saved) passwords and execute various commands.

Bozok is free, which increases the number of cyber criminals who could try to infect computers with it.

Bozok malware

Cyber criminals employ Bozok is to infect computers with other malware (by uploading and executing malicious files). They could install ransomware, other types of Trojans, cryptocurrency miners, and other malicious programs.

Bozok also allows cyber criminals to download files stored on the victim's computer including personal, sensitive documents (e.g., financial documents), which might contain confidential information, passwords, etc. Furthermore, this RAT can be used to start and kill processes.

For example, to end processes of running computer security software and prevent Bozok from being detected and/removed by it. Furthermore, this malware can be used to modify the registry. For example, to ensure that the program launches itself after a reboot, to hide itself, to integrate with existing legitimate processes, and so on.

Cyber criminals can also use it to steal stored passwords. In this way, they might be able to steal various accounts and use them for malicious purposes. For example, to make fraudulent purchases, transactions, trick other users into making money transactions, spread malware via email or other services, etc.

Additionally, Bozok can be used to download and load a DLL plugin, which extends its functionality with certain commands. Research shows that these commands can be used to start and stop a Virtual Network Computing (VNC) session, enable and disable the webcam, start and stop keylogging, and perform other tasks.

In summary, having Bozok installed on your computer could cause problems such as identity theft, monetary, data loss, installation of unwanted, malicious software, issues relating to online privacy, and other serious problems.

Threat Summary:
Name	Bozok Remote Administration Trojan
Threat Type	Trojan, password-stealing virus, banking malware, spyware.
Detection Names	BitDefenderTheta (Gen:NN.ZevbaF.34128.Cn0@a8DwJ0mO), ESET-NOD32 (A Variant Of Win32/GenKryptik.CMKB), Kaspersky (Trojan.Win32.Boht.akq), Microsoft (Trojan:Win32/Wacatac.C!ml), Full List (VirusTotal)
Malicious Process Name(s)	FastStone Capture (its name might vary).
Symptoms	Remote Administration Trojans are designed to stealthily infiltrate the victim's computer and remain silent, and thus no particular symptoms are clearly visible on an infected machine.
Distribution methods	Infected email attachments, malicious online advertisements, social engineering, software 'cracks'.
Damage	Stolen passwords and banking information, identity theft, the victim's computer added to a botnet.
Malware Removal (Windows)	To eliminate possible malware infections, scan your computer with legitimate antivirus software. Our security researchers recommend using Combo Cleaner. Download Combo Cleaner To use full-featured product, you have to purchase a license for Combo Cleaner. 7 days free trial available. Combo Cleaner is owned and operated by RCS LT, the parent company of PCRisk.com.

More examples of malware similar to Bozok (RATs) are DarkTrack, EpicSplit and VoidRAT. Commonly, this software does not appear in the list of running processes and programs, and so the cyber criminals responsible have a greater chance to use it for a longer period and cause more damage.

Therefore, it is important to take certain precautions to avoid installation of any RAT (or other malware) as described below.

How did Bozok infiltrate my computer?

Research shows that cyber criminals attempt to trick users into installing Bozok through phishing campaigns. They send emails that contain a malicious attachment to trick recipients into opening it. When opened, the attachment causes installation of Bozok.

Some examples of files that cyber criminals attach to their emails to spread malware are malicious Microsoft Office documents, executable files such as .exe, JavaScript files, PDF documents, archive files such as RAR, ZIP. Commonly, malware is also distributed using Trojans, dubious software download channels, unofficial activation tools and fake updaters.

Trojans are malicious programs that often spread (install) other malware, thereby causing chain infections, however, they must already be installed on computers. Untrusted channels are used to proliferate malware by disguising malicious files as harmless and regular.

When downloaded and opened/executed, the files install malware. Some examples of dubious download channels are free file hosting, freeware download websites, unofficial pages, Peer-to-Peer networks (e.g., torrent clients, eMule), and third party downloaders.

Unofficial activation tools are illegal programs that supposedly activate licensed software free of charge (bypass software activation), however, they often install malware instead.

People who attempt to activate software in this way often infect their computers inadvertently. Fake software updaters cause damage by installing malicious software rather than the updates/fixes, or by exploiting bugs/flaws of outdated software that is installed on the computer.

How to avoid installation of malware

Do not trust or open attachments or website links in irrelevant emails that are received from suspicious, unknown addresses, since the emails are often sent by cyber criminals who seek to trick recipients into installing malware. Installed software must be updated and activated only with implemented functions/tools that are designed by official software developers.

Third party, unofficial tools often cause installation of malicious programs. Furthermore, it is illegal to activate any licensed programs with unofficial activators ('cracking' tools). All files and programs should be downloaded only from official, trustworthy websites and via direct links.

Other channels (such as third party downloaders, Peer-to-Peer networks, unofficial sites) can be used to distribute malicious software.

The same applies to third party installers. Scan the operating system regularly for threats using reputable antivirus or anti-spyware software. If you believe that your computer is already infected, we recommend running a scan with Combo Cleaner Antivirus for Windows to automatically eliminate infiltrated malware.

Malicious Bozok process running in Task Manager as "FastStone Capture" (its name might vary):

bozok rat faststone capture malicious process in task manager

An example of a malicious MS Word document used to inject Bozok RAT into the system:

Malicious MS Word document designed to inject Bozok RAT into the system

How to remove malware manually?

Most trojan infections can be removed by running a full system scan with Combo Cleaner. The full manual procedure below is for cases where automatic removal failed, where you want to verify a scan caught everything, or where the threat has multiple persistence points.

Tools you'll need

Combo Cleaner Antivirus 7-days free trial

Recommended primary scanner. VB100 certified. The 7-day free trial is available.

Microsoft Defender Offline Free · built-in

Built into Windows. Boots to a clean environment to catch rootkits.

Process Explorer Free

From Microsoft Sysinternals. Better than Task Manager - shows full paths and signatures.

Autoruns Free

From Microsoft Sysinternals. Lists every place malware can persist on your system.

Microsoft Safety Scanner (MSERT) Free

Official Microsoft on-demand scanner. Always-current signatures - expires every 10 days.

Phase 1~ 5 min

Contain - limit the damage

Disconnect from the network

30 secNo tool needed

Unplug your Ethernet cable and turn off Wi-Fi. If you're on a laptop, the airplane-mode key works fastest.

Why this matters

Many trojans exfiltrate data - saved browser passwords, banking sessions, screenshots - and accept remote commands. Cutting the network stops both immediately. Keep it disconnected until Phase 4.

Boot into Safe Mode with Networking

3 min

Safe Mode loads a minimal set of drivers and stops most malware from auto-running. "With Networking" lets you download tools - re-enable Wi-Fi only after you've booted in.

Windows 11

Open Settings → System → Recovery. Click Restart now next to Advanced startup.

Your computer will restart into the "Choose an option" menu. Click Troubleshoot → Advanced options → Startup Settings → Restart. After the second reboot, press 5 or F5.

Run Windows 11 in Safe Mode with Networking

Windows 10

Click the Windows logo, hold Shift, click the Power icon and choose Restart. In the Choose an option screen, click Troubleshoot → Advanced options → Startup Settings → Restart. Press F5.

Windows 8

Go to the Start Screen, type Advanced, select Settings → Advanced startup options → Restart now → Troubleshoot → Advanced options → Startup settings → Restart → F5.

Note: Windows 8 reached end-of-life in January 2023 - running on it puts you at much higher risk of reinfection.

Windows 7

Click Start → Shut Down → Restart → OK. As the system boots, press F8 repeatedly until the Windows Advanced Options menu appears, then choose Safe Mode with Networking.

Note: Windows 7 reached end-of-life in January 2020 - running on it puts you at much higher risk of reinfection.

Phase 2~ 15 min

Identify - find what's hiding

Inspect running processes with Process Explorer

Tool: Process Explorer5 min

Download Process Explorer from Microsoft Sysinternals. Run it as Administrator. Click Options → Verify Image Signatures and View → Lower Pane View → DLLs.

Sort by "Verified Signer." Anything unsigned running from %AppData%, %LocalAppData%, %Temp%, or %ProgramData% is suspicious. Right-click → Properties to see the full image path. Right-click → "Search Online" to look up unfamiliar process names.

Why not just Task Manager

Task Manager hides full file paths, doesn't show digital signatures, and groups processes in ways that make malware easy to miss. Process Explorer is the same tool Microsoft engineers use.

Process Explorer showing a suspicious unsigned process running from %AppData%

Map every persistence point with Autoruns

Tool: Autoruns 14.x10 min

Download Autoruns. Right-click Autoruns.exe and choose Run as administrator - without elevation, Autoruns can't inspect protected registry hives.

In the menu, open Options → Hide Microsoft Entries and Options → Hide Empty Locations, then click Refresh.

Modern trojans don't just live in startup. Walk through these tabs and look for unsigned or unfamiliar entries:

Logon - classic Run/RunOnce keys
Scheduled Tasks - frequent hiding spot, especially tasks with PowerShell, MSHTA, or rundll32 actions
Services - unsigned services in non-Microsoft folders
WMI - Event Subscriptions are a stealthy persistence mechanism (MITRE T1546.003)
Image Hijacks - Image File Execution Options "Debugger" abuse
AppInit - DLLs loaded into every GUI process
Browser plug-ins - unsigned add-ons across all installed browsers

Pro tip

Right-click any suspicious entry → "Jump to Image" to see the actual file. Right-click → "Search Online" opens VirusTotal for the file hash. Don't delete yet - just write down the file paths and entry names. We'll remove them after the scans.

Autoruns 14.x with Hide Microsoft Entries enabled showing the Logon and Scheduled Tasks tabs

Check the hosts file and DNS settings

3 minBuilt into Windows

Trojans often redirect bank, antivirus, and update domains to attacker-controlled servers by editing the hosts file or DNS settings.

Hosts file: Open Notepad as Administrator and open C:\Windows\System32\drivers\etc\hosts. Legitimate entries are commented with #. Any uncommented IP-to-domain mapping is suspicious - especially redirects for microsoft.com, windowsupdate, or your bank.

DNS settings: Open Command Prompt as Administrator and run ipconfig /all. Confirm your DNS servers point to your ISP, your router, or a known public resolver (Cloudflare 1.1.1.1, Google 8.8.8.8). Then open Settings → Network & internet → [your adapter] → DNS server assignment and verify both DNS and DNS over HTTPS (DoH) settings haven't been hijacked.

Why this matters

A clean PC with hijacked DNS is still a compromised PC. You'll think you're at chase.com and you'll be at the attacker's clone.

Phase 3~ 60-90 min

Remove - three scans, one cleanup

No single antivirus catches everything. The order below is intentional: offline scan first (catches rootkits before Windows fully loads), then on-demand scanners on the running system, then manual cleanup of anything they missed.

Run Microsoft Defender Offline

Tool: Built into Windows15 min

Reboot to normal Windows. Open Windows Security → Virus & threat protection → Scan options. Select Microsoft Defender Antivirus (offline scan) and click Scan now. Your computer will restart into a stripped-down environment and scan before the full operating system loads.

Why this comes first

Rootkits and bootkits hide from any scanner running on the same Windows session that's already infected. A pre-boot offline scan sees the disk before the malware can hide itself.

Recommended antivirus

Combo Cleaner

VB100 certified. Includes anti-trojan, registry/persistence scanning, anti-spyware in one pass. The 7-day free trial is available.

Download Combo Cleaner

Run Combo Cleaner full system scan

Tool: Combo Cleaner20-40 min

Install Combo Cleaner and run a full system scan (not the quick scan). Let it complete fully, review the detected threats, and apply the recommended actions. Combo Cleaner will quarantine known trojans and registry persistence.

Combo Cleaner full scan results showing detected threats

Run Microsoft Safety Scanner as a second-opinion scan

Tool: Microsoft Safety Scanner15 min

Download Microsoft Safety Scanner (MSERT.exe), Microsoft's free on-demand tool. The binary expires every 10 days, which means every download has the latest signatures. Run a full scan after Combo Cleaner to catch anything one engine alone might miss.

Why a second scan

Different scanning engines catch different threats. Running an additional Microsoft scan after Combo Cleaner is the single most underused verification step in malware removal.

Manually remove anything still listed in Autoruns

Tool: Autoruns10 min

Reopen Autoruns. Anything you flagged in Step 4 that's still present hasn't been caught by the automated scans. For each remaining suspicious entry: right-click → Delete in Autoruns (this removes the persistence registration), then navigate to the file path and delete the actual file. Empty the Recycle Bin.

Important

Some malware files reappear after deletion because something else on the system recreates them. If you delete a file and it returns within minutes, you have a remaining persistence point that Autoruns didn't show - usually a service or scheduled task running under SYSTEM. Re-run the scans from Steps 6-8 or proceed to a clean install (see end of guide).

Phase 4~ 15 min

Recover - restore browsers and security

Reset browsers and clear notification permissions

5 min

Trojans and adware frequently hijack browsers - change the default search engine, install rogue extensions, or grant themselves notification permissions to keep displaying scam pop-ups even after the malware is gone.

Chrome: visit chrome://settings/reset and click "Restore settings to their original defaults." Then visit chrome://settings/content/notifications and remove any unfamiliar sites.
Edge: visit edge://settings/reset. Then check edge://settings/content/notifications.
Firefox: open about:support and click Refresh Firefox (Firefox uses "Refresh," not "Reset"). Then check Settings → Privacy & Security → Permissions → Notifications.

Review installed extensions in each browser and remove anything you don't recognize, especially extensions you didn't install yourself.

Re-enable Defender, Tamper Protection, and update everything

10 min

Many trojans disable security software. Open Windows Security → Virus & threat protection → Manage settings and confirm Real-time protection, Cloud-delivered protection, and Tamper Protection are all turned on. Tamper Protection prevents malware from disabling Defender silently.

Then run Windows Update (Settings → Windows Update → Check for updates) and update your browsers and applications. The infection vector that let the trojan in originally usually involves outdated software.

Phase 5~ 15 min + 7 days

Verify & secure

Change passwords from a clean device

20 min⚠ Critical

If the trojan was an info-stealer (Lumma, RedLine, Vidar, and similar are extremely common), assume every password saved in your browser is compromised. Change them from a different, known-clean device - your phone is fine if it's not infected.

Recommended order:

Primary email first - it's the recovery hub for everything else
Banking and financial accounts
Password manager master password (if you use one)
Social media, shopping, and remaining accounts

Where available, enable phishing-resistant multi-factor authentication (passkeys / FIDO2 hardware keys / authenticator apps) - SMS-based MFA is bypassable by sophisticated attackers.

Verify the clean and monitor for 7 days

5 min + 1 week monitoring

Reconnect to the network and run one final full scan with Combo Cleaner. Open Task Manager (Ctrl + Shift + Esc) and switch to the Startup apps tab - confirm nothing suspicious has reappeared.

Over the next 7 days, watch for symptom recurrence: unexpected high CPU usage, unknown processes returning, browser redirects, or pop-ups. If anything returns, you missed a persistence point and the procedure needs to be repeated - or you may have a deeper compromise that requires a clean install.

Verifying malware removal in the Windows 11 Task Manager Startup apps tab

When to clean install Windows instead

Manual removal isn't always the right answer. Reinstalling Windows from scratch is the only way to be 100% certain when:

The malware reappears after every removal attempt
A bootkit or UEFI rootkit was detected (this class of threat sits below the operating system and survives a normal Windows reinstall)
A confirmed credential-theft trojan ran with administrator privileges (Lumma, RedLine, Vidar) - the system likely has multiple unknown payloads
The PC is used for online banking, business email, or anything where partial doubt isn't acceptable

A clean install is a 30-60 minute process: Windows 11 reinstall via Settings → System → Recovery → Reset this PC → Remove everything → Cloud download. Back up documents to external storage first, scan the backup with Combo Cleaner before restoring it, and reinstall applications fresh - never restore them from a backup of the infected system.

Important: Manual removal requires advanced computer skills. If you're not confident identifying system files from malicious files, run an automated scan with Combo Cleaner and Windows Defender and stop there - that path catches the vast majority of consumer trojans without the risk of breaking Windows by deleting the wrong file.