How to protect computers from infection by the Stalk worm

Also Known As: Worm.Win32 Stalk
Type: Trojan
Damage level: Severe

What is Stalk?

Stalk (also known as Worm.Win32 Stalk) is a malicious program categorized as a 'worm'. Typically, worms automatically spread to other computers and work to infect as many systems as possible. The payload of this worm is unknown, however, it could be used to proliferate a number of malicious programs.

To avoid detection, Stalk hides the "Show hidden files and folders" option by making changes to the Windows registry.

Stalk malware

Research shows that cyber criminals distribute Stalk by disguising various files as textbooks of essays. When opened, they install this worm, which copies itself to the c:\z\ folder within which is also stores the desktop.ini and csrss.exe files. To proliferate itself on other computers, it might store these files in removable drives (such as USB).

If used, the drives proliferate Worm.Win32 Stalk (or Stalk) further. One possible scenario is when this worm is used to spread malware such as ransomware. Ransomware-type programs lock files by encrypting them with strong encryption algorithms.

Users of infected computers are unable to access their files unless they decode them with decryption software and/or a key that can only be purchased from the cyber criminals who designed ransomware. In summary, to recover files, ransomware victims are forced to pay a ransom.

Another possible payload is an information stealer, which could be designed to steal logins, passwords of accounts relating to banking, emails, and so on. Typically, cyber criminals use these programs to steal sensitive details that can be used to make fraudulent transactions, purchases, or generate revenue in other ways.

Furthermore, Stalk can be used to infect computers with a cryptocurrency miner. Cyber criminals seek to infect other computers with miners to use their hardware (GPU, CPU) to mine cryptocurrency. Users of infected systems usually receive higher electricity bills, since programs of this type force computers to consume more power.

Furthermore, high CPU and GPU usage can cause unexpected shutdowns that can lead to loss of unsaved data. Miners can also cause hardware to overheat and other problems.

Stalk could be used to install high-risk malware, thereby causing problems with privacy, browsing safety, financial/data loss, and other serious issues. If you suspect Stalk is installed on your computer, remove it immediately.

Threat Summary:
Name Worm.Win32 Stalk
Threat Type Worm
Payload Stalk could be used to spread a password-stealing virus, banking malware, spyware, ransomware, and other malware.
Symptoms Worms 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 files that are disguised as textbooks and/or essays, malicious online advertisements, social engineering, software 'cracks'.
Damage Stolen banking information, passwords, identity theft, victim's computer added to a botnet, additional installation of various malware.
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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Other examples of worms are Retadup and Forbix. These programs replicate - i.e., proliferate further from one infected computer to another. They can be used to infect systems with additional malware, thus causing serious problems. It is important to avoid installation of worms and all other malware.

How did Stalk infiltrate my computer?

This worm proliferates itself through infected drives (such as USB), however, at least one computer must be already infected with it. To proliferate malware, cyber criminals use emails (spam campaigns), Trojans, untrustworthy software download sources, software 'cracking' tools and fake updaters.

Emails can lead to installation of malware through attachments. Typically, cyber criminals attach Microsoft Office documents, archive files (ZIP, RAR), executables (.exe files), PDF documents, JavaScript, and other files. Their main goal is to trick recipients into opening the attached file, which then installs specific malware.

Another way to proliferate malicious programs is through Trojans. Once installed, these open 'backdoors' for other threats.

I.e., they cause chain infections/install additional malware. Untrustworthy download sources such as free file hosting, freeware download websites, Peer-to-Peer networks such as torrent clients, eMule and other similar channels can be used to disguise malicious files (executable .exe files) as legitimate.

People who use such channels risk download of malicious files. If opened, these install malicious software. Unofficial activation/'cracking' tools are used by some people to activate licensed programs free of charge, however, they often distribute malware/install unwanted, malicious software.

Fake software updaters infect computers when they install malicious programs rather than updates, or they exploit bugs, flaws of outdated, vulnerable software that is installed on the operating system.

How to avoid installation of malware?

Do not trust emails that are received from suspicious, unknown addresses. If they contain attachments or web links, they should not be opened, otherwise they might lead to installation of malware. All programs and files should be downloaded from official websites.

No other tools can be trusted (cyber criminals use them to distribute malicious programs). Installed programs must be updated properly using tools or functions provided by official developers (and not third party tools). If software is not free, it should not be activated using unofficial, 'cracking' tools.

These can be used to proliferate malware and are illegal. Keep systems safe from malicious programs by scanning them for viruses regularly using reputable anti-virus or anti-spyware software. 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.

Instant automatic malware removal: Manual threat removal might be a lengthy and complicated process that requires advanced IT 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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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 1 Download 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 the "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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