How to uninstall Covid21 malware?

Also Known As: Covid21 MBR Malware
Type: Trojan
Distribution: Low
Damage level: Severe

Covid21 virus removal guide

What is Covid21?

Covid21 is a coronavirus-themed malware that corrupts the MBR (The Master Boot Record) - the first sector on a startup drive that contains an executable code that works as a loader for the operating system. Simply said, it Covid21 prevents users from accessing the Windows operating system. Also, it changes victim's desktop wallpaper.

Covid21 malware message displayed by Covid21

It is common that attackers design malware like Covid21 to display a ransom demanding message with instructions on how to pay for a tool that supposed to restore the access to the operating system. However, this particular malware does not display any ransom note. It displays an image of a character from Japanese manga with a message saying that "Windows is killed". It is important to mention that even if Covid21 would display a ransom demanding message, there would be no guarantee that attackers would provide a tool (or tools) that supposed to restore access Windows.

Threat Summary:
Name Covid21 MBR Malware
Threat Type MBR malware
Detection Names Avast (Win32:Malware-gen), BitDefender (Dropped:Application.Joke.Blurscrn.A), ESET-NOD32 (A Variant Of Win32/KillMBR.NDS), Kaspersky (Trojan.Win32.DiskWriter.dtu), Microsoft (Trojan:Win32/Killmbr), Full List (VirusTotal)
Symptoms Windows operating cannot be accessed, changed desktop wallpaper
Distribution methods Infected email attachments, malicious online advertisements, social engineering, software 'cracks'.
Damage Corrupted MBR (Master Boot Record)
Malware Removal (Windows)

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In conclusion, cyber criminals behind Covid21 do not demand to be paid or contacted, for this reason it is very likely that this malware is still under development. Also, it is possible that an upgraded (demanding ransom) version of the Covid21 will be released in the future. It is unknown how the current Covid21 version is distributed, however, it is very likely that cyber criminals use one (or more) of the ways that are described in the paragraphs below.

How did Covid21 infiltrate my computer?

In most cases cyber criminals use malspam, unreliable software download sources, Trojans, fake software updating tools and unofficial activation ('cracking') tools to distribute malware. Malspam emails contain malicious attachments or download links for malicious files. Recipients install malware when they download and open malicious attachments/files. Examples of files that could be used to deliver malware via email are malicious Microsoft Office documents, PDF documents, archive files (like ZIP, RAR), JavaScript files and executable files (like .exe). Examples of unreliable file, software download sources are Peer-to-Peer (P2P) networks (like torrent clients, eMule), freeware download websites, third party downloaders, free file hosting pages. Their users infect computers when they download and open malicious files. Typically, those malicious files are disguised as harmless, regular.

Trojans can be designed to cause chain infections. Usually users get tricked in to installing them when they are disguised as legitimate programs. Once installed, those Trojans install additional malware. Fake software updating tools, if used, infect systems either by installing malicious software instead of updates, fixes for the installed software, or by exploiting bugs, flaws of installed software that is out of date. Unofficial activation ('cracking') tools are designed to illegally activate licensed software. Nevertheless, it is common for them do be designed not to bypass software activation but to install some malicious software.

How to avoid installation of malware?

Third party downloaders, installers, Peer-to-Peer networks (e.g., torrent clients, eMule) and other sources, tools of this kind should not be used neither to download or install any software. It should be downloaded only from official websites and via direct links. Irrelevant emails that are received from unknown, suspicious addresses and contain attachments (or web links) should not be trusted. It is common that cyber criminals use such emails to deliver malware. Installed software has to be updated and activated with tools or functions from its official developers. Third party, unofficial tools can be (and often are) malicious. Also, it is illegal to use unofficial activation tools to activate licensed software, or use pirated software. A computer should have a reputable antivirus or anti-spyware software installed on it. That software should be used to scan the system for threats regularly. If you believe that your computer is already infected, we recommend running a scan with Malwarebytes for Windows to automatically eliminate infiltrated malware.

Screenshot of the Covid21's desktop wallpaper:

covid21 malware desktop wallpaper

Instant automatic malware removal: Manual threat removal might be a lengthy and complicated process that requires advanced computer skills. Malwarebytes is a professional automatic malware removal tool that is recommended to get rid of malware. Download it by clicking the button below:
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How to remove malware manually?

Manual malware removal is a complicated task - usually it is best to allow antivirus or anti-malware programs to do this automatically. To remove this malware we recommend using Malwarebytes for Windows. If you wish to remove malware manually, the first step is to identify the name of the malware that you are trying to remove. Here is an example of a suspicious program running on a user's computer:

malicious process running on user's computer sample

If you checked the list of programs running on your computer, for example, using task manager, and identified a program that looks suspicious, you should continue with these steps:

manual malware removal step 1Download a program called Autoruns. This program shows auto-start applications, Registry, and file system locations:

screenshot of autoruns application

manual malware removal step 2Restart your computer into Safe Mode:

Windows XP and Windows 7 users: Start your computer in Safe Mode. Click Start, click Shut Down, click Restart, click OK. During your computer start process, press the F8 key on your keyboard multiple times until you see the Windows Advanced Option menu, and then select Safe Mode with Networking from the list.

Safe Mode with Networking

Video showing how to start Windows 7 in "Safe Mode with Networking":

Windows 8 users: Start Windows 8 is Safe Mode with Networking - Go to Windows 8 Start Screen, type Advanced, in the search results select Settings. Click Advanced startup options, in the opened "General PC Settings" window, select Advanced startup. Click the "Restart now" button. Your computer will now restart into the "Advanced Startup options menu". Click the "Troubleshoot" button, and then click the "Advanced options" button. In the advanced option screen, click "Startup settings". Click the "Restart" button. Your PC will restart into the Startup Settings screen. Press F5 to boot in Safe Mode with Networking.

Windows 8 Safe Mode with networking

Video showing how to start Windows 8 in "Safe Mode with Networking":

Windows 10 users: Click the Windows logo and select the Power icon. In the opened menu click "Restart" while holding "Shift" button on your keyboard. In the "choose an option" window click on the "Troubleshoot", next select "Advanced options". In the advanced options menu select "Startup Settings" and click on the "Restart" button. In the following window you should click the "F5" button on your keyboard. This will restart your operating system in safe mode with networking.

windows 10 safe mode with networking

Video showing how to start Windows 10 in "Safe Mode with Networking":

 

manual malware removal step 3Extract the downloaded archive and run the Autoruns.exe file.

extract autoruns.zip and run autoruns.exe

manual malware removal step 4In the Autoruns application, click "Options" at the top and uncheck "Hide Empty Locations" and "Hide Windows Entries" options. After this procedure, click the "Refresh" icon.

Click 'Options' at the top and uncheck 'Hide Empty Locations' and 'Hide Windows Entries' options

manual malware removal step 5Check the list provided by the Autoruns application and locate the malware file that you want to eliminate.

You should write down its full path and name. Note that some malware hides process names under legitimate Windows process names. At this stage, it is very important to avoid removing system files. After you locate the suspicious program you wish to remove, right click your mouse over its name and choose "Delete".

locate the malware file you want to remove

After removing the malware through the Autoruns application (this ensures that the malware will not run automatically on the next system startup), you should search for the malware name on your computer. Be sure to enable hidden files and folders before proceeding. If you find the filename of the malware, be sure to remove it.

searching for malware file on your computer

Reboot your computer in normal mode. Following these steps should remove any malware from your computer. Note that manual threat removal requires advanced computer skills. If you do not have these skills, leave malware removal to antivirus and anti-malware programs. These steps might not work with advanced malware infections. As always it is best to prevent infection than try to remove malware later. To keep your computer safe, install the latest operating system updates and use antivirus software.

To be sure your computer is free of malware infections, we recommend scanning it with Malwarebytes for Windows.

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About the author:

Tomas Meskauskas

Tomas Meskauskas - expert security researcher, professional malware analyst.

I am passionate about computer security and technology. I have an experience of over 10 years working in various companies related to computer technical issue solving and Internet security. I have been working as an author and editor for pcrisk.com since 2010. Follow me on Twitter and LinkedIn to stay informed about the latest online security threats. Contact Tomas Meskauskas.

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Malware activity

Global malware activity level today:

Medium threat activity

Increased attack rate of infections detected within the last 24 hours.

QR Code
Covid21 MBR Malware QR code
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