How to eliminate GuLoader from the operating system

Also Known As: GuLoader downloader
Type: Trojan
Distribution: Low
Damage level: Severe

GuLoader virus removal guide

What is GuLoader?

GuLoader is a malware downloader used by cyber criminals to proliferate various Remote Access Trojans (RATs) and other Trojan-type programs. They use GuLoader to infect computers with malicious programs that can be used to steal sensitive information, infect computers with other malware, and perform other actions to help cyber criminals generate revenue.

GuLoader malware

Research shows that GuLoader is used to proliferate various RATs and stealers (malicious programs that collect sensitive data). RAT programs give cyber criminals control over infected computers/operating systems and allow them to log keystrokes, download and execute various files, access webcams, microphones, take screenshots, monitor computing activity, manage (copy, rename, delete) files, and perform other actions. In most cases, cyber criminals attempt to steal credit card details, credentials (passwords, logins) of accounts, which can be used to make fraudulent purchases, transactions and generate revenue in other ways. RATs are commonly used to infect computers with other malware including ransomware. Furthermore, GuLoader is often used to infect computers with malicious programs that steal sensitive information. Cyber criminals behind information stealers usually target banking-related details, passwords, logins, data saved on clipboard, and other sensitive information. They attempt to infect operating systems with GuLoader to cause chain infections. I.e., infect computers with other malware that can help them to generate revenue. Victims of malware that is proliferated through GuLoader risk suffering monetary and/or data loss, becoming victims of identity theft, experiencing problems relating to online privacy, and other serious issues. Therefore, if GuLoader or its payload is already installed on the operating system, it should be eliminated immediately.

Threat Summary:
Name GuLoader downloader
Threat Type Malware downloader
Detection Names Avast (Win32:Trojan-gen), BitDefender (Trojan.GenericKD.33531900), ESET-NOD32 (A Variant Of Win32/Injector.EKYU), Kaspersky (Backdoor.MSIL.NanoBot.bbks), Full List (VirusTotal)
Payload GuLoader can be used to infect systems with Agent Tesla, FormBook, LokiBot, NetWire, Remcos, Vidar and other malicious programs
Symptoms Programs like GuLoader 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, data and/or monetary loss, problems with online privacy
Malware Removal (Windows)

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Some examples of malicious programs that cyber criminals can spread via GuLoader are Agent Tesla, FormBook, LokiBot, NetWire, Remcos and Vidar. They might also use this downloader to infect systems with other malicious programs. Their main goal is to gain access to personal information and accounts, or perform other actions that enable them to generate revenue in fraudulent ways.

How did GuLoader infiltrate my computer?

Cyber criminals commonly proliferate malicious programs through spam campaigns, dubious download channels, unofficial (fake) software updating tools, Trojans and software 'cracking' tools/unofficial activators. Spam campaigns are often used to trick recipients into infecting systems through malicious attachments (or web links that download malicious files). When opened, the files or attachments install malware. Examples of files that cyber criminals include/attach to their emails are Microsoft Office, PDF documents, archive files (e.g., RAR, ZIP), executable files (.exe) and JavaScript files. Peer-to-Peer networks (torrent clients, eMule), freeware download websites, free file hosting websites, third party downloaders, unofficial pages, etc., are also used to distribute malicious programs. Cyber criminals employ them to host malicious files that, if downloaded and opened/executed, infect operating systems with high-risk malware. Note that third party installers can also proliferate malware. Unofficial tools that supposedly update installed software can infect operating systems by exploiting bugs/flaws of outdated software, or by installing malicious software rather than updates and fixes. Trojans can cause damage only if they already installed. These malicious programs can open 'backdoors' for other malware. In this way, they cause chain infections. Software 'cracking' tools are used by people who seek to activate software free of charge (bypass activation), however, they often install malicious software instead.

How to avoid installation of malware

Website links and attachments that are presented in irrelevant emails should not be trusted, especially if the emails are sent from unknown, suspicious addresses. If there is a reason to believe that an email is untrusted, the best option is to simply ignore it and leave its contents unopened. Software should be downloaded from official websites and via direct download links. Third party downloaders, installers, unofficial pages and other channels/tools should not be used. Installed software must be updated and activated only with tools/functions provided by official developers. Third party updaters and activators can install malware. Furthermore, it is illegal to bypass activation of licensed software with third party tools. Keep operating systems safe by scanning them for viruses and other threats regularly. These scans should be performed with reputable antivirus or anti-spyware software. If you believe that your computer is already infected, we recommend running a scan with Malwarebytes for Windows to automatically eliminate infiltrated malware.

Appearance of a Coronavirus-related spam email used to spread GuLoader malware (attachment is a .gz archive, which contains the executable "QUOTE 2020.PDF.exe"):

Coronavirus-related spam email used to spread GuLoader

Text presented within this email:

Subject: URGENT NEED: U.S. Department of Health & Human Services/COVID-19 Face Mask/ Forehead thermometers

Due to the wild spread of COVID-19 all over the United States, the U.S. Department of Health & Human Services is in urgent demand of Face mask and forehead thermometers for it's citizens.

I will like if your company can supply us with the attached products list.


Awaiting your urgent reply.


Best regards.

Sheila Conley


U.S. Department of Health & Human Services
200 Independence Avenue, S.W.

Another spam email used to spread GuLoader malware:

GuLoader malware-spreading spam email (2020-05-12)

Screenshot of a malicious MS Excel document ("complete_3.xlsm") attached to this spam email:

Malicious MS Excel document used to inject GuLoader malware (2020-05-12)

Another spam email spreading an identical MS Excel document:

GuLoader malware-spreading spam email (2020-05-14)

Examples of Die Post-themed spam emails distributing GuLoader malware (the attachment is a link leading to a malicious executable):

GuLoader malware-distributing Die Post-themed spam email (sample 1) GuLoader malware-distributing Die Post-themed spam email (sample 2)

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.

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.

PCrisk security portal is brought by a company RCS LT. Joined forces of security researchers help educate computer users about the latest online security threats. More information about the company RCS LT.

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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
GuLoader downloader QR code
A QR code (Quick Response Code) is a machine-readable code which stores URLs and other information. This code can be read using a camera on a smartphone or a tablet. Scan this QR code to have an easy access removal guide of GuLoader downloader on your mobile device.
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