Remove Cosakos Ransomware

Every computer users are facing problems on how to properly deal with viruses if it was able to infect their PC. If people are having difficulties fixing virus contamination, what more if the threat involved is a dreaded ransomware or file-locking infection. It may take great efforts and effective tools to remove the virus, while dealing with locked files are far more difficult to address. This is the case if computer is infected with Cosakos. A variant of STOP ransomware family, which is known to be notorious in denying user’s access to their own data.

Cosakos showcases the same deployment skills as previous variants like Mogranos, Nelasod, and Access. They all utilize spam emails, malicious advertisements, cracked programs, and shady links to infect random web users. By masquerading as valuable file or program, Cosakos can easily deceived users to run the file that will actually initiate the virus payloads and start whatever attackers have designed for this thing to carry out.

Per observation of malware researchers, Cosakos initially drops various executable files on system folders and start-up locations. Following this is a thorough searching for usual files like documents, pictures, images, videos, spreadsheet, archives, databases, and so on. As its ultimate assault, Cosakos will encrypt these files with high-grade encryption techniques and generate unique key that matches with the information of local hardware (MAC Address of network device).

Screenshot image of Cosakos infected files

Cosakos will never let user to speculate on what kind of virus have infected the computer because it will leave a ransom note on every folder as .cosakos encrypted files are located. As stipulated on this text file, victims must pay $980 in exchange for the private key and decryption software. Without these, there is no other way to recover the encrypted data.

What was written may be true because at this point, decryption software that may fully restore .cosakos files to their previous format is not yet available. Hence, dealing with the cyber crooks is an unwise decision to solve this dilemma because victims are transacting with swindlers that usually do not deliver after receiving the payment.

How to Remove Cosakos Ransomware

Ransomware files are placed deeply into the system and on various locations, thus, thorough scanning is vital to totally remove Cosakos virus. Aside from our suggested tool, you may also run your own security program.

Though affected files may be impossible to decrypt due to complexity of the encryption, you can still try recovery method like alternative tool, Shadow Explorer or Previous Version as described below.

Stage 1: Scan the Computer with Anti-Malware Tool

1. Download free anti-malware scanner called MalwareBytes Anti-Malware.
Malwarebytes Anti-Malware Download Link (this will open a new window)

2. After downloading, install the program. It may run automatically or you have to double-click on the downloaded file MBSetup.exe.

3. Carry out the installation with default setup process.

4. After the installation process, click the Get Started button to launch the program.

5. Continue with the prompts until the main program opens.

6. On the main console, click on Scan to run most complete detection method to find hidden objects associated to Cosakos ransomware.

7. Scanning may take a while. Please wait until the anti-malware tool is done with the checking.


8. Once the scan has completed, the tool will display the list of detected threats. Remove all identified malicious items and restart the computer if necessary.

Stage 2: Double-check for Cosakos’s leftover with Microsoft’s Malicious Software Removal Tool

1. Download the free scanner called Malicious Software Removal Tool.
Malicious Software Removal Tool Download Link (this will open a new window)


2. The tool automatically checks the operating system and suggest appropriate download version. Click on Download button to begin. Save the file to a convenient location, preferably on Desktop.

3. After downloading the file, Windows will prompt that download has completed. Click Run to start scanning for Cosakos ransomware. Another option is to browse the location folder and double click on the file to run.


4. The tool will display Welcome screen, click Next. Please note the message “This tool is not a replacement for an antivirus product.” You must understand that this program is made specifically to find and remove malware, viruses, Trojans, and other harmful elements on the computer. It was not designed to protect the computer.


5. Next, you will see Scan Type. Please choose Full Scan to ensure that all Cosakos ransom virus entities and other harmful files left on the computer will be found and removed. For advanced computer user, you can opt for Customized Scan, if there are other drives or folders you wanted to include in this scan.


6. Full scan may take a while, please wait for Malicious Software Removal Tool to complete the tasks. However, you may cancel the scan anytime by clicking on the Cancel button.


7. After scanning, the tool will reveal all identified threats. There may be other threats that our first scan fails to detect. Please remove/delete all detected items.

8. When removal procedure is complete, you may now close Malicious Software Removal Tool. We hope that Cosakos ransomware have been completely deleted from the computer. Please restart Windows to proceed with the normal operation.

Stage 3 : Unlocking files with Cosakos Decryption Tool

So far, this Cosakos decryption tool works only for files that were encrypted using offline keys. This happens sometimes if the virus is unable to communicate to remote server to obtain unique keys; instead, it will use offline keys when encrypting files. However, there is a little chance of recovering files using this tool due to limited available offline keys that were integrated with this decryption tool.

For additional information (download link, supported versions, instructions) about StopDecrypter, please proceed to ransomware decryption tool archive page.

If you received a message stating that “No keys were found for the following IDs (.cosakos)”, please copy and submit the information to the official download page to include your information (log file) and have it archive in case decryption software becomes available.

StopDecrypter Information

We will update this section once the full decryption tool is on hand. In the meantime, please try other options below.

Option 1: Windows Previous Version Tool

Windows Vista and Windows 7 have a feature called Previous Versions. However, this tool is only usable if restore point was made prior to Cosakos ransomware infection. To use this tool and recover files affected by the virus, please follow these steps:

1. Open My Computer or Windows Explorer.

2. Right-click on the affected files or folders. From the drop-down list, please click on Restore previous versions.

3. New window will open display all backup copy of files and folders you wanted to recover. Choose the appropriate file and click on Open, Copy, or Restore. Restoring selected files overwrites the current encrypted files on the computer.

Option 2: Use ShadowExplorer to restore files encrypted by Cosakos Ransomware

Just like Previous Version tool, ShadowExplorer is taking advantage of shadow copy created by Windows. This tool allows you to retrieve older version of files before it was encrypted by Cosakos ransomware.

1. Download ShadowExplorer from the official web site.

2. Install the program with the default settings.

3. The program should run automatically after installation. If not, double-click on ShadowExplorer icon.

4. You can see the drop-down list on top of the console. Please select proper drive and the most recent point-in-time shadow copies of files you wish to restore prior to Cosakos ransomware infection.


5. Right-click on the Drive, Folder, or File you wish to restore and click Export…

6. Lastly, ShadowExplorer will prompt for location where you want to save the copy of recovered files.

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2 thoughts on “Remove Cosakos Ransomware”

  1. Help me, Stopdecrypter does not work in my case. It scans the whole drive and shows done but files are not decrypting. I have very useful documents. Please help me.

  2. @Junaid, the download pages shows that Casakos in not yet supported by StopDecrypter. Please wait for a while.

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