How to remove viruses and malware spread through Facebook Messenger

What is "Facebook Messenger virus"?

"Facebook Messenger virus" was discovered by Ido Naor. Cyber criminals use it to spread FormBook, a trojan-type program, by sending various files through Facebook Messenger. If opened, these files cause installation of the aforementioned malicious program.

Facebook Messenger virus overview

Typically, people receive these files from their Facebook friends who have installed unwanted (malicious) programs that send spam. In our example, the file attached to the Messenger message is "video_13925.bz". This archive contains another file ("play_75367031.mp4.com") that can be extracted with 7-Zip. If opened, it downloads and installs the FormBook Trojan.

This program steals personal data. Using it, cyber criminals can record keystrokes and clipboard data, take screenshots, steal saved passwords/logins, and so on. Some of the stolen data might include banking details. Cyber criminals use all stolen data to generate revenue.

Their victims usually experience problems relating to finances (financial loss), browsing safety, privacy and other issues. FormBook might also be used to cause download and installation of other programs, and thus victims could have their computers infected with other malicious programs such as ransomware. If a computer is infected with FormBook, it should be removed immediately.

Trojan examples

FormBook is just one of many trojan-type programs. Examples of other similar malicious programs include Adwind, TrickBot, Tefosteal, and LokiBot. Trojans usually steal confidential, personal data/information and to proliferate other infections. Having a computer infected by them usually leads to serious problems.

How did "Facebook Messenger virus" infect my computer?

In this particular case, to proliferate FormBook, cyber criminals use Facebook Messenger. They use accounts of people who have malicious programs installed on their computers. Their accounts are used to proliferate FormBook simply by sending attached files that, if extracted and opened, cause computer infections.

There are also other ways to proliferate these malicious programs. For example, using spam campaigns, Trojans, fake software updating tools, software 'cracking' tools and various dubious software download sources. To trick people into installing unwanted programs (or computer infections) though spam campaigns, criminals send emails that contain malicious attachments.

Attached files are usually Microsoft Office, PDF documents, archives (ZIP, RAR, and others), executables, JavaScript files, and so on. If opened, they download and install malicious programs. Trojans are programs designed to proliferate other infections. When installed, they cause chain infections.

Fake (unofficial) software updating tools usually download and install unwanted programs (malware) rather than updates, fixes or they exploit bugs/flaws of outdated software. Software 'cracking' tools are programs that allow users to avoid paying for software activation, however, cyber criminals often use them to proliferate computer infections.

Rather than bypassing activation, these tools often download and install malicious programs. P2P (Peer-to-Peer) networks, free file hosting websites, freeware download websites, unofficial pages, third party downloaders, and other similar sources can be used to proliferate malware.

Typically, malicious files (executables) are presented as legitimate. By downloading and opening them, people often install unwanted programs and cause computer infections.

How to avoid installation of malware?

Be careful with attachments or web links received from unknown, suspicious addresses. If the email subject and context is irrelevant, do not open the attachment. Use official and trustworthy sources to download software. The aforementioned tools are not the safest ways to achieve this.

It is important to update installed software using implemented functions and tools provided/designed by official software developers. If installed software requires paid activation, it should not be performed using a 'cracking' tool. These are illegal and often cause installation of malicious programs.

Having a reputable anti-virus or/and anti-spyware software installed is also important. These tools can detect and remove various threats before they can proliferate or do any damage. If you have already opened "Facebook Messenger virus" attachment, we recommend running a scan with Combo Cleaner Antivirus for Windows to automatically eliminate infiltrated malware.

Screenshot of files attached to a message (placed on the Desktop) and the FormBook process disguised as "Service Host: Local System" in Task Manager:

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)

What is the Facebook Messenger virus?

"Facebook Messenger virus" refers to malicious spam messages distributed through the Facebook Messenger. These messages include variously named archive files containing malware, notably the FormBook malicious program. However, this spam could be used to proliferate other harmful programs (e.g., trojans, ransomware, cryptocurrency miners, etc.). It has to be emphasized that Facebook is in no way associated with this virus, and is merely abused as a tool to spread malware.

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

Most malicious programs can be removed without such drastic measures.

What are the biggest issues that malware can cause?

The threats posed by malware depend on its abilities and the attackers' goals. For example, FormBook (spread via Facebook Messenger virus) can steal a wide variety of sensitive information and cause chain infections. Generally, malware infections can lead to decreased system performance or failure, data loss, hardware damage, severe privacy issues, financial losses, and identity theft.

What is the purpose of malware?

Malware is typically used to generate revenue. However, cyber criminals may also use malicious programs to amuse themselves, disrupt processes (e.g., websites, services, companies, organizations, etc.), carry out personal vendettas, and launch politically/geopolitically motivated attacks.

Will Combo Cleaner protect me from malware?

Yes, Combo Cleaner is designed to detect and remove threats. It can eliminate most of the known malware infections. However, it must be emphasized that high-end malicious software tends to hide deep within systems - hence, performing a full system scan is paramount.