Cobalt Strike Malware (W32/Cobalt) - What is It and How to Remove It

by Ventsislav Krastev | December 4, 2017 | 0 Comments JavaScript, malware

Threat Summary Cobalt Strike Malware – Infection Analysis Cobalt Strike Malware – Malicious Activity How to Remove Cobalt Strike Malware from Your PC

This article aims to explain what is Cobalt Strike malware, how does it infect computers and how to remove it effectively from your computer.

New form of malware has been reported to cause infections via a vulnerability for Windows Machines that is 17 years old. The virus, related to the pen-testing (penetration testing) tool Cobalt Strike is also dubbed Cobalt Strike malware and it’s primary goal after infecting your computer is to turn it into a slave of the hackers who are behind the infection. In the event that you have seen W32/Cobalt or other similar detection on your computer, we recommend that you read this article and learn how to fully remove the Cobalt Strike malware from your PC and protect it against future infections and intrusions.

Threat Summary

Name	Cobalt Strike Malware, also known as PUP.DllInject.G
Type	JavaScript Malware Infection
Short Description	Aims to make your computer remotely controlled via shell commands by the hackers behind the virus.
Symptoms	No symptoms so far as the malware is file-less, but your computer may behave strange and can contain other malware in it.
Distribution Method	Via malicious URLs or compromised websites.
Detection Tool	See If Your System Has Been Affected by malware Download Malware Removal Tool
User Experience	Join Our Forum to Discuss Cobalt Strike Malware.

Cobalt Strike Malware – Infection Analysis

In order to cause a successful infection, the malicious file of this virus is actually a semi-legitimate Microsoft Word document, which pretends to be a legitimate file sent by a bank or a big company. The file itself infects via malicious macros which contain the exploit CVE-2017-11882 that is over 17 years old at the time of writing this. So far, what is known about this vulnerability is that it was only patched once, two weeks after it was discovered by Microsoft.

The way the cyber-criminals who are believed to be the Cobalt hacker group have decided to use malicious macro infections for their attacks in e-mails that they pretend are from Visa. One sample was detected by malware researchers Jasper Manual and Joie Salvio at Fortinet and it uses the following e-mail:

The message (In Russian) pretends to come from Visa’s payWave system and it aims to get the victim to open what appears to be a .zip and .doc files that pose as “New security system changes in Visa payWave”. Once this document is opened, the victim sees a legitimate Microsoft Word file that only says the words “Enable Editing”:

In reality however, the file triggers a script for PowerShell which initiates the download of the infection file of Cobalt Strike, while obfuscating it with the CVE-2017-11882 vulnerability. The whole process of initiating the download is done by taking control of the Microsoft HTML Application Host also known as the process mshta.exe, that has a purpose to execute HTML apps. The result of this is that the mshta.exe service connects to the IP address 104.254.99.77 and downloads the JavaScript infection payload of Cobalt Strike on the victim’s computer. But what is downloaded is not the final JavaScript payload, but instead this JavaScript triggers another download from the host 104.254.99.77 which downloads a file with a random name and the .ps1 suffix on the victim’s computer. The file is located in the %AppData% directory and may appear like the following:

→ %AppData%\28dh32d9233.ps1

When this .ps1 file is executed, the actual Cobalt Strike infection takes place on the victim’s computer.

Cobalt Strike Malware – Malicious Activity

Once downloaded, the .ps1 file, belonging to Cobalt Strike is automatically activated. It triggers yet another PowerShell script which has the client DLL files of Cobalt Strike – a rather outdated, but still very effective tool, previously used for penetration testing of the defenses in Windows Operating Systems. Once it detects whether your Windows is running based on 32-bit or 63-bit architecture, the appropriate Cobalt Strike DLL is executed directly in your Windows PowerShell memory and this results in the malware not being actually present on your drive, while remaining embedded in PowerShell and even if you delete the .ps1 file, the virus is still active on your PC. This also helps any antivirus programs that are conventional to detect the virus.

Once the DLL of Cobalt Strike is triggered, the cyber-criminals have obtained complete control of your computer system – it belongs to them. They can perform all of the activities which can be performed using the Cobalt Strike shell commands themselves. Here is only a small part of commands that may be triggered, using Cobalt malware:

→ spawnto – spawns sessions into processes.
inject – injects various malicious scripts in legitimate Windows processes.
dllinject – same as inject but for DLLs
download – can download other malware or files on your computer.
upload – can upload files to the hacker’s server, i.e. it can steal your files.
timestomp – to assist with blending files, obfuscation and updating itself.
ls – similar to Linux, it helps you to list different files.
mkdir – to create folders on your computer.
keylogger pid – to log your keystrokes.
screenshot pid – to take a screenshot of your desktop.
jobkill – to kill a job.
socks 8080 – to set a Proxy server on a selected port (in this case 8080).

These are only the main commands that are likely to be used on your computer and you have no way of knowing that they are triggered as it all happens in the background of your computer. The full list of commands can be seen on Cobalt Strike’s web page.

How to Remove Cobalt Strike Malware from Your PC

In order to remove this malware, you will need to have some experience in Working with Windows PowerShell and definitely some malware removal experience. So if manual removal is not your type of thing to do, security experts strongly recommend to use an advanced malware removal tool instead of conventional antivirus program. Such software will not only automatically scan for and remove Cobalt Strike malware from your computer, but will also make sure that your computer stays protected against other JavaScript and PowerShell infections in the future.

Ventsislav Krastev

Ventsislav is a cybersecurity expert at SensorsTechForum since 2015. He has been researching, covering, helping victims with the latest malware infections plus testing and reviewing software and the newest tech developments. Having graduated Marketing as well, Ventsislav also has passion for learning new shifts and innovations in cybersecurity that become game changers. After studying Value Chain Management, Network Administration and Computer Administration of System Applications, he found his true calling within the cybersecrurity industry and is a strong believer in the education of every user towards online safety and security.

How to Remove Cobalt Strike Malware from Windows.

Step 1: Boot Your PC In Safe Mode to isolate and remove Cobalt Strike Malware

OFFER

Manual Removal Usually Takes Time and You Risk Damaging Your Files If Not Careful!

We Recommend To Scan Your PC with SpyHunter

Keep in mind, that SpyHunter’s scanner is only for malware detection. If SpyHunter detects malware on your PC, you will need to purchase SpyHunter's malware removal tool to remove the malware threats. Read our SpyHunter 5 review. Click on the corresponding links to check SpyHunter's EULA, Privacy Policy and Threat Assessment Criteria

1. Hold Windows key() + R

2. The "Run" Window will appear. In it, type "msconfig" and click OK.

3. Go to the "Boot" tab. There select "Safe Boot" and then click "Apply" and "OK".

Tip: Make sure to reverse those changes by unticking Safe Boot after that, because your system will always boot in Safe Boot from now on.

4. When prompted, click on "Restart" to go into Safe Mode.

5. You can recognise Safe Mode by the words written on the corners of your screen.

Step 2: Uninstall Cobalt Strike Malware and related software from Windows

Here is a method in few easy steps that should be able to uninstall most programs. No matter if you are using Windows 10, 8, 7, Vista or XP, those steps will get the job done. Dragging the program or its folder to the recycle bin can be a very bad decision. If you do that, bits and pieces of the program are left behind, and that can lead to unstable work of your PC, errors with the file type associations and other unpleasant activities. The proper way to get a program off your computer is to Uninstall it. To do that:

1. Hold the Windows Logo Button and "R" on your keyboard. A Pop-up window will appear.

2. In the field type in "appwiz.cpl" and press ENTER.

3. This will open a window with all the programs installed on the PC. Select the program that you want to remove, and press "Uninstall"

Follow the instructions above and you will successfully uninstall most programs.

Step 3: Clean any registries, created by Cobalt Strike Malware on your computer.

The usually targeted registries of Windows machines are the following:

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnce
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce

You can access them by opening the Windows registry editor and deleting any values, created by Cobalt Strike Malware there. This can happen by following the steps underneath:

1. Open the Run Window again, type "regedit" and click OK.

2. When you open it, you can freely navigate to the Run and RunOnce keys, whose locations are shown above.

3. You can remove the value of the virus by right-clicking on it and removing it.

Tip: To find a virus-created value, you can right-click on it and click "Modify" to see which file it is set to run. If this is the virus file location, remove the value.

IMPORTANT!
Before starting "Step 4", please boot back into Normal mode, in case you are currently in Safe Mode.
This will enable you to install and use SpyHunter 5 successfully.

Step 4: Scan for Cobalt Strike Malware with SpyHunter Anti-Malware Tool

1. Click on the "Download" button to proceed to SpyHunter's download page.

Download

Malware Removal Tool

It is recommended to run a scan before purchasing the full version of the software to make sure that the current version of the malware can be detected by SpyHunter. Click on the corresponding links to check SpyHunter's EULA, Privacy Policy and Threat Assessment Criteria.

2. After you have installed SpyHunter, wait for it to update automatically.

3. After the update process has finished, click on the 'Malware/PC Scan' tab. A new window will appear. Click on 'Start Scan'.

4. After SpyHunter has finished scanning your PC for any files of the associated threat and found them, you can try to get them removed automatically and permanently by clicking on the 'Next' button.

If any threats have been removed, it is highly recommended to restart your PC.

Windows Mac OS X Google Chrome Mozilla Firefox Microsoft Edge Safari Internet Explorer Stop Push Pop-ups

Get rid of Cobalt Strike Malware from Mac OS X.

Step 1: Uninstall Cobalt Strike Malware and remove related files and objects

OFFER

Manual Removal Usually Takes Time and You Risk Damaging Your Files If Not Careful!

We Recommend To Scan Your Mac with SpyHunter for Mac

Keep in mind, that SpyHunter for Mac needs to purchased to remove the malware threats. Click on the corresponding links to check SpyHunter’s EULA and Privacy Policy

1. Hit the ⇧+⌘+U keys to open Utilities. Another way is to click on “Go” and then click “Utilities”, like the image below shows:

2. Find Activity Monitor and double-click it:

3. In the Activity Monitor look for any suspicious processes, belonging or related to Cobalt Strike Malware:

Tip: To quit a process completely, choose the “Force Quit” option.

4. Click on the "Go" button again, but this time select Applications. Another way is with the ⇧+⌘+A buttons.

5. In the Applications menu, look for any suspicious app or an app with a name, similar or identical to Cobalt Strike Malware. If you find it, right-click on the app and select “Move to Trash”.

6: Select Accounts, after which click on the Login Items preference. Your Mac will then show you a list of items that start automatically when you log in. Look for any suspicious apps identical or similar to Cobalt Strike Malware. Check the app you want to stop from running automatically and then select on the Minus (“-“) icon to hide it.

7: Remove any left-over files that might be related to this threat manually by following the sub-steps below:

Go to Finder.
In the search bar type the name of the app that you want to remove.
Above the search bar change the two drop down menus to “System Files” and “Are Included” so that you can see all of the files associated with the application you want to remove. Bear in mind that some of the files may not be related to the app so be very careful which files you delete.
If all of the files are related, hold the ⌘+A buttons to select them and then drive them to “Trash”.

In case you cannot remove Cobalt Strike Malware via Step 1 above:

In case you cannot find the virus files and objects in your Applications or other places we have shown above, you can manually look for them in the Libraries of your Mac. But before doing this, please read the disclaimer below:

Disclaimer! If you are about to tamper with Library files on Mac, be sure to know the name of the virus file, because if you delete the wrong file, it may cause irreversible damage to your MacOS. Continue on your own responsibility!

1: Click on "Go" and Then "Go to Folder" as shown underneath:

2: Type in "/Library/LauchAgents/" and click Ok:

3: Delete all of the virus files that have similar or the same name as Cobalt Strike Malware. If you believe there is no such file, do not delete anything.

You can repeat the same procedure with the following other Library directories:

→ ~/Library/LaunchAgents
/Library/LaunchDaemons

Tip: ~ is there on purpose, because it leads to more LaunchAgents.

Step 2: Scan for and remove Cobalt Strike Malware files from your Mac

When you are facing problems on your Mac as a result of unwanted scripts and programs such as Cobalt Strike Malware, the recommended way of eliminating the threat is by using an anti-malware program. SpyHunter for Mac offers advanced security features along with other modules that will improve your Mac’s security and protect it in the future.

Click the button below below to download SpyHunter for Mac and scan for Cobalt Strike Malware:

Download

SpyHunter for Mac

Windows Mac OS X Google Chrome Mozilla Firefox Microsoft Edge Safari Internet Explorer Stop Push Pop-ups

Remove Cobalt Strike Malware from Google Chrome.

Step 1: Start Google Chrome and open the drop menu

Step 2: Move the cursor over "Tools" and then from the extended menu choose "Extensions"

Step 3: From the opened "Extensions" menu locate the unwanted extension and click on its "Remove" button.

Step 4: After the extension is removed, restart Google Chrome by closing it from the red "X" button at the top right corner and start it again.

Windows Mac OS X Google Chrome Mozilla Firefox Microsoft Edge Safari Internet Explorer Stop Push Pop-ups

Erase Cobalt Strike Malware from Mozilla Firefox.

Step 1: Start Mozilla Firefox. Open the menu window

Step 2: Select the "Add-ons" icon from the menu.

Step 3: Select the unwanted extension and click "Remove"

Step 4: After the extension is removed, restart Mozilla Firefox by closing it from the red "X" button at the top right corner and start it again.

Windows Mac OS X Google Chrome Mozilla Firefox Microsoft Edge Safari Internet Explorer Stop Push Pop-ups

Uninstall Cobalt Strike Malware from Microsoft Edge.

Step 1: Start Edge browser.

Step 2: Open the drop menu by clicking on the icon at the top right corner.

Step 3: From the drop menu select "Extensions".

Step 4: Choose the suspected malicious extension you want to remove and then click on the gear icon.

Step 5: Remove the malicious extension by scrolling down and then clicking on Uninstall.

Windows Mac OS X Google Chrome Mozilla Firefox Microsoft Edge Safari Internet Explorer Stop Push Pop-ups

Remove Cobalt Strike Malware from Safari.

Step 1: Start the Safari app.

Step 2: After hovering your mouse cursor to the top of the screen, click on the Safari text to open its drop down menu.

Step 3: From the menu, click on "Preferences".

Step 4: After that, select the 'Extensions' Tab.

Step 5: Click once on the extension you want to remove.

Step 6: Click 'Uninstall'.

A pop-up window will appear asking for confirmation to uninstall the extension. Select 'Uninstall' again, and the Cobalt Strike Malware will be removed.

How to Reset Safari
IMPORTANT: Before resetting Safari make sure you back up all your saved passwords within the browser in case you forget them.

Start Safari and then click on the gear leaver icon.

Click the Reset Safari button and you will reset the browser.

Windows Mac OS X Google Chrome Mozilla Firefox Microsoft Edge Safari Internet Explorer Stop Push Pop-ups

Eliminate Cobalt Strike Malware from Internet Explorer.

Step 1: Start Internet Explorer.

Step 2: Click on the gear icon labeled 'Tools' to open the drop menu and select 'Manage Add-ons'

Step 3: In the 'Manage Add-ons' window.

Step 4: Select the extension you want to remove and then click 'Disable'. A pop-up window will appear to inform you that you are about to disable the selected extension, and some more add-ons might be disabled as well. Leave all the boxes checked, and click 'Disable'.

Step 5: After the unwanted extension has been removed, restart Internet Explorer by closing it from the red 'X' button located at the top right corner and start it again.