How to get rid of msaRAT malware

What kind of malware is msaRAT?

msaRAT is a Remote Access Trojan (RAT) written in the Rust programming language, linked to the Chaos ransomware group. According to research published by Talos Intelligence, it uses an unusual "living off the browser" technique to keep its communications with the attacker's server hidden.

Rather than making network connections on its own, msaRAT takes control of a Chrome or Edge browser already installed on the victim's machine and routes all attacker traffic through it. This makes the malware's activity look like ordinary browser usage, which is considerably harder for security tools to detect.

The RAT is delivered as an MSI installer that impersonates a routine Windows update. Victims typically notice nothing unusual at the point of infection.

msaRAT overview

Once the installer runs, msaRAT loads its payload directly into memory and searches for a Chrome or Edge browser on the system using environment variable checks and Windows Registry queries. Once located, the browser is launched silently in headless mode with remote debugging enabled.

With the browser under its control, msaRAT can capture screenshots of the victim's screen, execute commands on the machine, and send files back to the attacker. The connection is persistent, meaning the attacker retains access to the infected machine and can issue new instructions at any time.

The "living off the browser" technique

msaRAT communicates with the attacker's server by sending instructions to the hijacked browser using Chrome DevTools Protocol (CDP), a built-in debugging interface present in Chrome and Edge. The browser then injects JavaScript into its own session and opens an encrypted data channel to the attacker.

The data channel is built on WebRTC - a technology browsers normally use for video calls and file sharing. msaRAT forces all traffic through a Twilio relay server, so the attacker's real IP address never appears directly in network logs.

Traffic also passes through Cloudflare's infrastructure, masking its origin further. The communications themselves are protected by two encryption layers: WebRTC provides one automatically, and msaRAT adds a second using ChaCha20-Poly1305 with keys negotiated via Elliptic-curve Diffie-Hellman.

How msaRAT avoids detection

Because all outbound connections appear to come from the browser process and not from the malware itself, security tools that monitor unknown programs making external connections will not observe msaRAT directly on the network. The real attacker infrastructure is hidden behind Cloudflare's content delivery network and Twilio's relay servers.

msaRAT also disables Content Security Policy in the browser session it controls via a CDP command, and spoofs HTTP request headers to make traffic appear to originate from a Microsoft service. HTTP traffic is sent over port 443, the port normally associated with HTTPS, which can help it slip past firewalls that check port numbers rather than actual protocols.

Conclusion

msaRAT is a technically sophisticated RAT used by the Chaos ransomware group to maintain covert remote access to infected machines. Its browser-based C2 technique makes it considerably harder to detect than conventional RATs, as all traffic appears to come from a legitimate browser rather than from the malware itself.

An infection puts victims at risk of data theft, remote surveillance, and the deployment of additional payloads, including ransomware. The malware should be removed from any affected system without delay. More examples of RATs are Dolphin X, MarkiRAT, and Starland.

How did msaRAT infiltrate my computer?

According to Talos Intelligence, msaRAT is delivered as an MSI installer file named update_ms.msi. It is downloaded via a curl command over HTTP on port 443 and disguised as a routine Windows update, which reduces the victim's suspicion at the moment of installation. Once the installer runs, the RAT payload is loaded directly into memory.

The Chaos group, active since February 2025, targets large organizations and threatens to both encrypt their data and leak it publicly unless a ransom is paid. The group has been observed gaining initial access through spam emails and voice phishing calls, with remote management tools used to maintain persistence and legitimate file-sharing services used to exfiltrate stolen data.

More broadly, RATs and similar threats reach victims through phishing emails with malicious attachments, fake software download pages, pirated software and software 'cracks', malicious advertisements, and infected removable storage devices. Downloading software only from official sources significantly lowers the risk of infection.

How to avoid installation of malware?

Be cautious with any unexpected email, particularly one containing an attachment or link. Even messages that appear to come from a trusted sender can be spoofed. Download programs only from official developer websites or trusted app stores, and avoid pirated software, 'cracks', and key generators.

Keep your operating system and all installed applications up to date to close known security vulnerabilities. Use reputable security software and run regular scans. 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 msaRAT malware, should I format my storage device to get rid of it?

Formatting your storage device will remove msaRAT, but it will also delete every file on the drive. Running a trusted security program such as Combo Cleaner is the better first step, since it can eliminate the infection without wiping your data.

What are the biggest issues that msaRAT malware can cause?

msaRAT gives attackers remote control over the infected machine, allowing them to capture screenshots, run commands, and steal files. Since it operates within the Chaos ransomware ecosystem, an infection can also serve as a precursor to ransomware deployment, putting all stored data at risk.

What is the purpose of msaRAT malware?

msaRAT is designed to give the Chaos ransomware group covert remote access to infected computers. Operators can execute commands, capture screenshots, and exfiltrate files, and the persistent connection can be used to deliver further payloads at any time.

How did msaRAT malware infiltrate my computer?

msaRAT has been observed spreading as a fake Windows update - an MSI installer file pushed via a curl command. The Chaos group also uses spam emails and voice phishing to gain initial access. More broadly, threats of this kind reach victims through phishing emails, fake download sites, and pirated software.

Will Combo Cleaner protect me from malware?

Yes. Combo Cleaner can detect and remove most known malware, including Remote Access Trojans. Because sophisticated threats can embed themselves deeply in a system, running a full scan is the best way to ensure the infection is fully cleared.