CoViper Malware

What is the CoViper malware?

CoViper is yet another Coronavirus/COVID-19-themed malware infection, most likely proliferated as a file related to the pandemic. It operates by rewriting the system Master Boot Record (MBR). It does not delete the original, but rather creates a backup and replaces it with a custom MBR.

Typically, malicious software that modifies MBRs do so to prevent the Operating System (OS) from being booted (i.e., started). It also displays a screen-encompassing message, often containing a ransom message - this disables user access to the device. Such malicious programs are categorized as MBRLockers/screenlockers or ransomware.

In the case of CoViper, it does not make any demands, such as ransoms, however, there is evidence to suggest that this malware is still in development and may be updated for these purposes in future.

CoViper malware displayed message during system boot

CoViper creates various files (full list below) in the temporary folder "%TEMP%" (typically, the path is "C:\Users\[username]\AppData\Local\Temp\"). It then creates a new hidden folder named "COVID-19" in the victim's home directory and copies these files into it.

Users are presented with a window, the message therein stating that "Coronavirus" has been successfully installed and the device will be restarted in five seconds to finish installation. After five seconds has elapsed, the malicious program reboots the system and executes three of its files ("end.exe", "run.exe" and "Update.vbs").

The "end.exe" file rewrites the MBR, which stops the OS from booting normally. Instead, during any subsequent reboots, users are greeted with a message stating that their computer has been "trashed" and lists an account on the Discord communication app.

During the first reboot, CoViper disables Windows Task Manager, changes the desktop wallpaper and mouse cursor. Once the system is booted, "run.exe" initiates the "mainWindow.exe" process, which displays a window containing an image of the COVID-19 virus.

The window contains two buttons: "Help" and "Remove virus". The latter is disabled, however, its presence suggests that, should CoViper be updated, it may be used for ransom purposes. The former button ("Help") displays a pop-up window, which states that victims are seeing this message since their system has been infected with the Coronavirus.

It states that trying to close this window with Task Manager is a waste of time, as it has been disabled. When users attempt to restart the system, due to the custom MBR, it cannot be booted and they are presented with the previously mentioned boot message.

Despite this, a solution was discovered by Avast cybersecurity - by pressing "CTRL+ALT+ESC" key combination, the original MBR is reinstated and users can access their device as usual. This does not resolve all of the issues, but does allow people to successfully boot their computer.

Antivirus software must then be run to scan the system and remove all files related to CoViper. Note that "Update.vbs" is unfinished and, at the time of research, is a defunct feature of this malware.

As its name implies, it is designed to keep CoViper up to date, and thus it is likely that any current infections are merely test runs and the malicious program might be released with improved functionality later. Regardless, CoViper must be immediately removed from the system in its entirety.

Threat Summary:
Name	CoViper virus
Threat Type	Trojan, password-stealing virus, banking malware, spyware.
Detection Names	Avast (FileRepMalware), BitDefender (Trojan.GenericKD.42887639), ESET-NOD32 (BAT/Agent.OWN), Kaspersky (HEUR:Trojan.Win32.Generic), Full List (VirusTotal)
Symptoms	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.

Malware has a wide variety of malicious capabilities/functions.

It can lock the device screen (as is the case with Rubly, StalinLocker, etc.), download/install additional malware (e.g. GuLoader, Buerak, etc.), allow remote access and control over the infected machine (e.g. FireBird, BlackNix, etc.), encrypt data and demand ransom payments (e.g. MSPLT, WANNACASH NCOV, etc.), steal private and highly sensitive information (e.g. Laturo, KPOT, etc.), mine cryptocurrency (e.g. BitCoinMiner, XMR Miner, etc.) and so on.

Whatever their functionalities, these malicious programs have just one purpose: to generate revenue for the cyber criminals using them.

The presence of this software on devices can compromise system integrity and damage it, resulting in permanent data loss, leading to financial losses, severe privacy issues and even identity theft. Therefore, eliminate all malware infections without delay.

How did CoViper infiltrate my computer?

CoViper has been observed being spread via an executable file named "COVID-19.exe" (other filenames are possible). While the exact distribution methods are unknown, it is most likely proliferated using Coronavirus/COVID-19 related scams.

Recently, there has been an influx of MBRLockers similar to CoViper, many of which do not demand ransom payments for restoration of the damage caused (potentially, due to being tested or as callous "pranks"). These malicious programs have been known to spread through sharing of an infectious file (e.g. "COVID-19.exe") via the Discord application.

In general, malware is commonly proliferated using 'backdoor' Trojans, spam campaigns, illegal activation tools ("cracks"), rogue updates and untrustworthy download channels. Some Trojans have the capability to cause chain infections (i.e., download/install additional malware).

Spam campaigns are used to send deceptive/scam emails on a mass scale. These messages are usually disguised as "official", "important", "urgent" and similar. They have infectious files attached to (or linked inside) them. Infectious files can be in various formats (e.g. archive and executable files, Microsoft Office and PDF documents, JavaScript, etc.).

When they are executed, run or otherwise opened, the infection process is triggered. Rather than activating licensed products, "cracking" tools can download/install malicious software. Fake updaters cause infections by exploiting weaknesses of outdated products and/or simply by installing malware rather than the updates.

Malicious content can be unintentionally downloaded from untrusted sources such as unofficial and free file-hosting sites, Peer-to-Peer sharing networks and other third party downloaders.

How to avoid installation of malware

Suspicious or irrelevant emails should not be opened, especially those containing attachments or links, as this can result in an infection. This applies to files/links shared by unknown/suspect senders on other communication platforms as well. Use only official and verified download channels.

You are advised to activate and update products with tools/functions provided by legitimate developers. Illegal activation tools ("cracks") and third party updaters should be avoided, as they are often used to spread malware. To ensure device and user safety, it is crucial to have a reputable anti-virus/anti-spyware suite installed and kept up to date.

Use this software for regular system scans and removal of detected threats/issues. 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.

File related to CoViper malware:

coronavirus.bat - installs the malicious program and ensures its persistence;
end.exe - rewrites the Master Boot Record (MBR);
run.exe - starts the mainWindow.exe process;
mainWindow.exe - displays a window with the image of the Coronavirus;
Update.vbs - defunct script, most likely originally conceived to update the malware;
cursor.cur - cursor file that is set as the new cursor's appearance;
wallpaper.jpg - the new desktop wallpaper that is set as the default.

Text presented in message, displayed via custom MBR:

Created By Angel Castillo. Your Computer Has Been Trashed.

Discord: Windows Vista#3294

Screenshot of the window, displayed after the malicious executable of CoViper is opened:

CoViper malware pop-up displayed after the malicious executable is opened

Text presented in this message:

Administrator: coronavirus installer
Coronavirus sucessfully installed!
Your computer will restart in 5 seconds to finish the installation :)

Screenshot of the window, displayed after the first system reboot:

CoViper malware pop-up displayed after the first restart

Text presented in this window:

Hello! If you see this message is because your computer has infected by coronavirus! Please don't wast your time, Task Manager are disabled and you can't terminate this process! If you close this window, it will appear again! so, one more time, DON'T WAST YOUR TIME!

OK

Help

Remove virus

Appearance of another Master Boot Record (MBR)-modifying malware infection (might also be called Red Mist Squidward virus) developed by the same cyber criminal. The malware is virtually the same - the main differences are displayed in a pop-up window and a slightly different message within the modified MBR.

As with CoViper, this variant also supports the "CTRL+ALT+ESC" key combination, which reinstates the original MBR and allows users to boot the system properly:

MBR-hijacking malware identical to CoViper

Text presented within this modified MBR:

Created By Angel Castillo. Your Computer Has Been Trashed.

Screenshot of the pop-up window displayed after the first reboot:

A pop-up displayed by a MBR-hijacking malware identical to CoViper

Text presented within the pop-up:

Help

Hi! if you see this message is because your PC have been infected by the Red Mist Squidward virus! If you reboot your PC, it will not be able to boot again!

Update 18 May 2020 - The developer of CoViper has released yet another similar malware infection, which also behaves in a very similar manner.

Screenshot of the pop-up displayed once the malicious executable is opened:

CoViper variant first pop-up

Text presented within:

Executing this program will destroy your computer. If you are an antivirus tester or virus tester you can use this program. No way to fix your computer after infection. Do not run this on your main PC, use a virtual machine. Windows 7, 8, 8.1, 10 are able to run this virus. This virus will destroy your computer if you accept the rules and creator won't be responsible for any damage made by this program. If you are trying this on a real machine, you are responsible. If you do not want to infect your PC, please press "Cancel".

I accept everything. I am responsible

Coded by Angel Castillo/Windows Vista

Screenshot of the second pop-up:

CoViper variant second pop-up

Text presented within:

coronavirus has infected your PC!

Hello! If you see this message is because your PC have been infected by coronavirus trojan! Say goodbye to your PC because actually there's no way to remove this virus hahaha!
Do you want to see the screen of rules?
Show Rules Nah!
*When setup is finished, your PC will restart automatically
Windows Vista#3294 contact.windows.vista@gmail.com

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.