Also Known As: RustyBuer malware
Type: Trojan
Damage level: Severe


One of the most commonly used ways to deliver malware is to send emails with malicious links or files (attachments) in them. Cybercriminals behind this particular email attempt to trick users into downloading and opening a malicious document designed to install RustyBuer.



Typically, emails containing malicious links or attachments look like they came from a financial institution, a government agency, or other legitimate entity (company, organization). This email is disguised as a letter sent by American Medicine Publicity.

As stated in the email letter, it contains urgent information from CDC (Centers for Disease Control and Prevention) and FDA (Food and Drug Administration) regarding vaccines against COVID-19 disease. It encourages recipients to review the attached document, which supposedly contains detailed information (such as possible contraindications, complications, prices) about vaccines available in the US.

As mentioned in the first paragraph, the file attached to this email is malicious - it is designed to infect computers with RustyBuer. RustyBuer functions as a loader malware - it can be used to install other malware.

It is known that cybercriminals RustyBuer have already used it to distribute Cobalt Strike Beacon and multiple ransomware strains. This malware can be used to download and execute malware in different ways.

Thus, opening the malicious document attached to this email is likely to cause the installation of malware designed to encrypt files, provide cybercriminals remote access to the infected machine, steal sensitive information, or cause other damage.

Threat Summary:
Name RustyBuer malware
Threat Type Malware loader
Hoax Attachment contains information about COVID-19 vaccines
Attachment(s) document.xlsm (its name may vary)
Detection Names (Attachment) Avast (Other:Malware-gen [Trj]), BitDefender (Trojan.GenericKD.37150109), Emsisoft (Trojan.GenericKD.37150109 (B)), Ikarus (Trojan-Downloader.Office.Crypt), Microsoft (TrojanDownloader:O97M/EncDoc.SS!MTB), Full List Of Detections (VirusTotal)
Symptoms Malware loaders are designed to stealthily infiltrate the victim's computer and remain silent, and thus no particular symptoms are clearly visible on an infected machine.
Payload RustyBuer
Distribution methods Infected email attachments, malicious online advertisements, social engineering, software 'cracks'.
Damage Stolen passwords and banking information, identity theft, data loss.
Malware Removal (Windows)

To eliminate possible malware infections, scan your computer with legitimate antivirus software. Our security researchers recommend using Combo Cleaner.
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Malspam campaigns in general

In conclusion, cybercriminals behind emails of this type pretend to be legitimate companies, organizations to trick recipients into downloading and opening a malicious file. Usually, attachments in malicious emails are disguised as important, official documents.

More examples of malspam campaigns are "Olmetex Email Virus", "Santander Email Virus", and "Contech Email Virus". Examples of malware that is distributed via email (and possibly other channels) are FormBook, LokiBot, and Agent Tesla.

How did URGENT INFORMATION ON COVID-19 VACCINATION email virus infect my computer?

The file attached to this email is a malicious Microsoft Excel document that needs permission to enable content (macros commands) to install RustyBuer. It installs RustyBuer after getting that permission.

It is important to mention that malicious documents opened with Microsoft Office versions released before 2010 do not need permission to enable macros commands to install malware - they install malicious software automatically. Newer MS Office versions prevent malware installation by opening documents in "Protected View" mode.

It is worth mentioning that malicious emails can contain PDF documents, JavaScript files, executable files, archive files (like ZIP, RAR), and other files as well. In one way or another, the main purpose of those emails is to trick recipients into executing a malicious file.

How to avoid installation of malware?

Attachments and website links in irrelevant emails received from suspicious, unknown senders should not be opened. It is very common for emails of this type to be used by cybercriminals as channels to deliver malware.

Installed programs have to be updated and activated properly: it should be done using implemented functions or tools that their official developers provide. Third-party, unofficial tools can be malicious (have malware hidden in them). Also, it is illegal to use cracked software or use cracking tools to activate legitimate software.

Furthermore, programs and files should be downloaded from official, trustworthy websites and via direct links. It is not recommended to use third-party downloaders or installers, unofficial pages, and other channels of this kind to download or install any software.

The operating system should be scanned for threats regularly. It is recommended to do it using a reputable antivirus or anti-spyware software. If you've already opened URGENT INFORMATION ON COVID-19 VACCINATION email attachment, we recommend running a scan with Combo Cleaner Antivirus for Windows to automatically eliminate infiltrated malware.


Subject: COVID-19 Vaccination information


This email contains urgent information on latest researches from CDC and FDA in the field of vaccines against COVID-19.

Internal statistics from CDC and FDA on lethal cases and illness after vaccination (read more in attached file), we have not fully studied their real danger. Wide selection of vaccines offer has created illusion of security and feeling that we have a choice.

Studies have shown that possibility of getting infected COVID-10 after a vaccine significantly increases, and also leads to complications in the form of infertility, development of diseases of lungs and central nervous system, and even blindness.

Some prisons have unofficially introduced vaccines to prisoners, those sentenced to life sentences or death penalty. Outbreaks of COVID-19 diseases and even deaths account for areas where people were massively vaccinated. You can avoid risk of getting infected by untested vaccines.

CDC and FDA together have compiled a complete summary of contraindications, chances of death outcome, and complications from use of available vaccines in the US (such as Pfizer-BioNTech, Moderna, Johnson & Johnson / Janssen, etc.) and other countries, as well as the price you will pay for them. Compare conditions under which certain vaccines are not suitable for you, as well as those which are contraindicated for children, pregnant women, elderly people, people with chronic diseases and allergy sufferers. Information valid as of May 2021.

You were assigned personal access to the attached document, your pass code: ohpfdpfjlqysasyl

Sent by American Medicine Publicity, 250 Willow Drive San Pablo, CA 94806,
info@cov19inf.com Unsubscribe

Malicious attachment distributed via URGENT INFORMATION ON COVID-19 VACCINATION email:

Malicious attachment distributed through URGENT INFORMATION ON COVID-19 VACCINATION email

Instant automatic malware removal: Manual threat removal might be a lengthy and complicated process that requires advanced computer skills. Combo Cleaner 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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Quick menu:

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 Combo Cleaner Antivirus 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 Combo Cleaner Antivirus 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.

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