How to remove Brook malware from the operating system

What kind of malware is Brook?

Brook is a Remote Administration Trojan (RAT) built using the versatile Go programming language. It is a sophisticated tool with the added capability of extracting sensitive information. This combination of stealth and power makes Brook a formidable threat in the realm of cybersecurity, capable of infiltrating systems and discreetly siphoning off valuable data.

More about Brook

Brook possesses a formidable array of capabilities. Among its arsenal lies the insidious ability to monitor and meticulously log keystrokes. This functionality enables Brook to covertly record user inputs, providing cybercriminals with a comprehensive insight into sensitive information such as passwords, credit card details, and other confidential data.

Also, Brook can capture desktop screenshots. With this insidious functionality, Brook surreptitiously seizes snapshots of the victim's desktop, granting cybercriminals a visual window into the user's activities. This invasive capability further enhances Brook's ability to gather sensitive information.

Furthermore, this malware can collect and manipulate clipboard data. This nefarious ability allows Brook to intercept any information copied to the clipboard by the user, including passwords, sensitive documents, and other confidential data. Moreover, Brook can replace the clipboard's contents.

In the hands of cybercriminals, its ability to replace clipboard contents becomes a powerful tool for executing cryptocurrency theft. By intercepting clipboard data, Brook can identify instances where users copy cryptocurrency wallet addresses for transactions. Subsequently, it stealthily replaces these legitimate wallet addresses with those controlled by the attackers, redirecting cryptocurrency payments to their wallets.

Also, the malware employs API hooking to intercept system functions, enabling manipulation of applications and the operating system. Additionally, Brook employs advanced techniques to detect debugging tools and virtual machine environments, ensuring its evasion of analysis and detection efforts.

Furthermore, Brook demonstrates its stealthy nature by employing tactics such as introducing delays in execution using the Windows API Sleep function. This delay enhances its ability to evade detection by security tools and analysts. Moreover, it conducts a systematic enumeration of files, directories, and running processes, gathering vital system information for surveillance and exploitation.

Brook's prowess extends to querying system details, terminating processes, and extracting sensitive data like usernames and passwords from URLs. Additionally, Brook manipulates security tokens using the AdjustTokenPrivileges function, bypassing restrictions to execute malicious actions with elevated privileges.

To facilitate efficient data exfiltration, it sends collected information, including system details and harvested data, to a designated Telegram bot.

Conclusion

In essence, Brook's capabilities underscore its status as a formidable threat in the ever-evolving landscape of cybersecurity, posing significant challenges to defenders and users alike. Brook requires a multi-faceted approach, including proactive defense strategies, continuous monitoring, and awareness of emerging attack vectors to mitigate impact and safeguard against potential breaches.

Examples of other RATs are DarkMe, AllaKore, and Xeno.

How did Brook infiltrate my computer?

Threat actors often devise deceitful emails to deceive recipients into opening malicious attachments or links. Upon opening those attachments or links, malware can swiftly infiltrate the victim's system. Another common method of dissemination is malvertising, where attackers embed malicious code within online advertisements.

Merely visiting a compromised webpage can also initiate the download of malware. Additionally, threat actors may exploit vulnerabilities within outdated software or operating systems. Alternatively, computers may fall prey to infection through pirated software, downloads sourced from peer-to-peer networks, and other unreliable channels.

How to avoid installation of malware?

Make sure to keep your operating system and software applications up to date. Install reliable antivirus or anti-malware software and regularly scan the system. Be cautious when handling suspicious emails from unknown addresses, especially those containing attachments or links. Avoid visiting untrustworthy websites and interacting with pop-ups or advertisements displayed on them.

When downloading software and files, use reputable sources such as official app stores or the developer's website. Avoid downloading pirated or cracked software to reduce the likelihood of malware infections. 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.

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

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1

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.

2

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.

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

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3

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.

4

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.

5

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

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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.

6

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

7

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.

8

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.

9

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

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10

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.

11

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

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12

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:

1. Primary email first - it's the recovery hub for everything else
2. Banking and financial accounts
3. Password manager master password (if you use one)
4. 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.

13

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.

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.

Frequently Asked Questions (FAQ)

My computer is infected with Brook malware, should I format my storage device to get rid of it?

Eliminating the malware by formatting your storage device can be a viable solution. Nonetheless, it is imperative to recognize that this action will obliterate all data stored on the device. Therefore, before initiating the formatting process, it is essential to attempt to remove the malware by utilizing a trusted security tool.

What are the biggest issues that malware can cause?

Malware can cause significant issues, including the theft of sensitive data, disruption of system functionality, financial losses, privacy breaches, or data loss.

What is the purpose of Brook malware?

The purpose of Brook malware is to infiltrate and compromise computer systems for various malicious activities, including remote administration, data theft, and surveillance, ultimately enabling cybercriminals to gain unauthorized access, gather sensitive information, and potentially execute further attacks.

How did a malware infiltrate my computer?

Malware likely infiltrated your computer through malicious email attachments, infected websites, or software downloads from untrusted sources. It could also have exploited vulnerabilities in outdated software or operating systems or through the use of infected removable storage devices like USB drives. Pirated software, cracking tools, and key generators are other common vectors.

Will Combo Cleaner protect me from malware?

Combo Cleaner has the ability to detect and eliminate nearly all known malware infections. It is crucial to recognize that sophisticated malware frequently hides deeply within the system. Thus, performing a thorough system scan is imperative to ensure effective detection and removal.