Avoid clicking on the link in the Customer Complaint Report malspam

Also Known As: Cobalt Strike
Type: Trojan
Distribution: Low
Damage level: Severe

Customer Complaint email virus removal guide

What is Customer Complaint email virus?

It is common for cybercriminals to use emails as channels to trick users into downloading and installing malware on their computers. Emails that are used to deliver malware are called phishing emails or malspam. Usually, these emails contain a malicious attachment or some website link that opens a download page for a malicious file. It is important to mention that cybercriminals behind malspam/phishing emails pretend to be legitimate companies. They also disguise their emails as important, official and (or) urgent. This particular email is used to deliver Cobalt Strike.

Customer Complaint email virus malware-spreading email spam campaign

This is a targeted and personalized malspam campaign. It mentions the company name of its recipient. It is disguised as a letter from the HR department and claims that someone has filed a customer complaint against its recipient. Moreover, it claims that a recipient will be fined two weeks' wages because of that. The main purpose of this email is to trick a recipient into reviewing the "complaint" - into clicking a website link which is designed to open a download page (e.g., Google Docs or another legitimate page, or a deceptive site) for a malicious executable file designed to install Cobalt Strike, a tool that cybercriminals use for various purposes, for example: to upload and download files, log keystrokes (record keyboard input), execute commands via Command Prompt, etc. Basically, the attackers use Cobalt strike to steal sensitive information (e.g., credit card details, login credentials, social security numbers, names, surnames) and to distribute (install) malware (e.g., Trojans, ransomware, cryptocurrency miners). Therefore, by clicking the link in this email and opening a downloaded file, recipients could encounter problems such as data, monetary loss, identity theft, loss of access to various personal accounts, issues with online privacy, browsing safety, and more.

Threat Summary:
Name Cobalt Strike
Threat Type Trojan, password-stealing virus, banking malware, spyware.
Hoax A customer complaint is filed against the recipient
Detection Names Avast (Win64:DangerousSig [Trj]), AVG (Win64:DangerousSig [Trj]), ESET-NOD32 (Win64/Rozena.BY), Kaspersky (Trojan.Win64.Shelma.iku), Microsoft (Backdoor:Win64/Bazarldr.MJK!MTB), Full List Of Detections (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.
Payload Cobalt Strike
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 Malwarebytes.
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More examples of malspam campaigns/phishing emails are "Here's your PayPal invoice Email Virus", "International Air & Sea Freight Forwarder Email Virus", and "Ministero Dello Sviluppo Economico Email Virus". As a rule, phishing emails are employed as tools to distribute malware or to extract sensitive information. In one way or another, falling for such scams can lead to serious problems. Therefore, it is strongly advisable to analyze suspicious emails before opening attachments or clicking links. Examples of malware that cybercriminals distribute via email are Agent Tesla, Emotet, LokiBot, and Ursnif.

How did Cobalt Strike infect my computer?

As a rule, recipients install malware on their computers when they download and open a malicious attachment or click on a link and then open a downloaded file. In this particular case, Cobalt Strike gets installed after executing a malicious executable file downloaded via the provided website link. It is worthwhile to mention that a link in this phishing email may open a legitimate website, for example, Google Docs page (docs.google[.]com). When cybercriminals use email attachments to distribute malware, they usually attach a malicious PDF or Microsoft Office document, JavaScript file, ZIP, RAR or another archive file, an executable file (like .exe). In most cases, malicious email attachments install malware once they are opened. However, documents opened with Microsoft Office (2010 or newer) do not infect computers unless users enable macros (editing or content). Malicious documents opened with older MS Office versions do not have the "Protected View" mode.

How to avoid installation of malware?

it is essential to carefully analyze emails that contain attachments or links. If an email attachment or website link is received from an unknown, suspicious sender,  then it should not be opened.  Especially if a received email is irrelevant. Also, it is important to download software from official, trustworthy sources and via direct links only and avoid using third-party downloaders like Peer-to-Peer networks, questionable, unofficial websites, and other similar sources for downloading files or programs. Furthermore, installed software that needs to be updated or activated should be activated or updated using tools or implemented functions that its official developers provide. It is never safe to use third party, unofficial tools for that - they often are bundled with malware. Moreover, it is against the law to activate licensed software with 'cracking' tools, or use pirated software. Lastly, a computer is safer if it has a reputable anti-virus or anti-spyware suite installed on it. It is advisable to run virus scans regularly and keep the security software up to date. If you've already opened "Customer Complaint email virus" attachment, we recommend running a scan with Malwarebytes for Windows to automatically eliminate infiltrated malware.

Text presented in the email:

Subject: [recipient's company name] complaint

By [recipient's company name] head office HR request, here is a copy of your Customer Complaint Report #852-2-25

You will get two weeks payout. I am very sorry for that.

Customer Complaint Report on you in PDF online: hxxps://customer-complaint-25febr.getresponsepages.com/

[recipient's company name] outsource HR assistant

Screenshot of the download page for the executable file that installs Cobalt Strike:

customer complaint report email virus deceptive website

Screenshot of the malicious file "Customer Statement.exe" (its name may vary) detected as a threat by multiple detection engines:

customer complaint report email virus attachment detections list on virustotal

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:
▼ DOWNLOAD Malwarebytes By downloading any software listed on this website you agree to our Privacy Policy and Terms of Use. To use full-featured product, you have to purchase a license for Malwarebytes. 14 days free trial available.

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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
Cobalt Strike 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 Cobalt Strike on your mobile device.
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