Cosw Virus

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*Cosw is a variant of Stop/DJVU. Source of claim SH can remove it.


Cosw is an exceptionally dangerous virus that falls into the category of file-encrypting ransomware. Cosw is one of millions of viruses of this type and its effects can prove devastating to its victims. Therefore, it is vital that this infection be treated with the utmost caution.

The Cosw ransomware will leave a _readme.txt file with instructions

Below we have included a detailed removal guide that will walk you through the steps necessary to remove this nasty virus from your computer. And in addition we have also included possible solutions to the encryption that Cosw has placed on your files. Be warned, however, that due to the very complex nature of this encryption and how this type of malware operates, a full recovery of the encrypted data may not be possible. We encourage you to read through this article and learn a little more about what this virus is like and what your options of handling it are.

The Cosw virus

The Cosw virus encrypts the files on infected computers using a complex two-part key. The Cosw virus then blackmails its victims into paying ransom to obtain the decryption key.

The hackers behind this type of malware like Coaq, Goaq normally try to scare their victims into paying by threatening to destroy the key after a certain period of time. Alternatively, they can tell you that the price will double or that your files will be permanently deleted, or something else along those lines.

And while they may keep their promise, it’s not a fact that they will actually send a decryption key even after you’ve made them. Usually, they hide behind the veil of anonymity provided by the cryptocurrency normally used a payment method. And that explains how ransomware like Cosw has become such a booming industry. Without the ability to trace the cyber criminals, they don’t fear persecution and they are basically free to spread these viruses and extort money from unsuspecting users.

As it so happens, ransomware is actually a multimillion dollar criminal scheme. And the only way to undermine it at this point is if victims refuse to pay ransom and seek alternative means of combating the infections. As pointed out, there are removal guides like the one before to help you delete Cosw, which you should do anyway, regardless of whether you choose to transfer the ransom payment or not. And there are also alternative ways to recover your files that won’t necessarily cost you anything.

The .Cosw file encryption

The .Cosw file encryption is a very complex one and not something that can easily be reversed. Users require a special decryption key to undo the .Cosw file encryption. And this is the key that the hackers promise to send in exchange for the ransom money.

The Cosw virus will encrypt your files

However, there are decryptor tools available online that can be able to help your situation. You just have to keep a lookout for them, as they do become available over time for the more “popular” ransomware variants. Alternatively, after you’ve removed Cosw you can try to extract copies of your files from system backups or a cloud or separate hard drive where you may have them stored.


Danger LevelHigh (Ransomware is by far the worst threat you can encounter)
Data Recovery ToolNot Available
Detection Tool

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*Cosw is a variant of Stop/DJVU. Source of claim SH can remove it.

Remove Cosw Ransomware

Step 1 of this removal guide explains how to boot the infected PC into Safe Mode. If you need help with that, we recommend that you begin the removal process by clicking on the Safe Mode link and following the on-screen instructions.

Please save this page to your browser’s bookmarks before you proceed, so that you don’t have to look for the Cosw removal instructions when your computer restarts.


*Cosw is a variant of Stop/DJVU. Source of claim SH can remove it.

Cosw is a stealthy ransomware version that is difficult to detect. A major challenge in dealing with this ransomware is finding and shutting down its harmful processes. In order to do that, follow these instructions step-by-step.

Using the computer’s keypad, press CTRL+SHIFT+ESC together. After that, search for any processes that appear to be linked to the danger. The Windows Task Manager’s Processes tab will let you view all processes that are running on the computer.

In case you find a process that looks suspicious, right-click on it and select Open File Location from the quick menu.

You can use the free online scanning tool provided below to confirm that the files connected with the dubious process are virus-free.

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    If the scanner discovers a danger in one of the scanned files, you may first want to end the process related to those files by right-clicking on it in the Processes tab and selecting End Process. After that, go back to the infected files’ original locations and remove them.

    Next, open System Configuration (type msconfig in the Windows search field and press Enter). In the next step, check out the Startup tab and the list of startup items.

    Disable any startup items that appear to be related with the malware. Also, search for startup components that aren’t related with the apps that normally start when the system boots up. If you locate enough information to support their deactivation, uncheck their checkboxes. However, make sure that no part of the operating system or trusted software is disabled.

    *Cosw is a variant of Stop/DJVU. Source of claim SH can remove it.

    In order to eradicate the ransomware and guarantee that it does not reemerge or leave behind any harmful components, you will need to erase any dangerous registry entries found in your registry editor.

    The Registry Editor can be launched by typing regedit in the Windows search field and pressing Enter. To find ransomware-related files in the Registry Editor, use the CTRL and F keyboard keys, type the threat’s name into the Find box, and then click Find Next. Right-clicking on a hazardous entry and selecting Delete will remove it from your system.

    Attention! Do not remove any other registry entries. Any additional registry changes or deletions that are unrelated to the attack components and entries may result in system or installed software damage. To avoid the risk, this post includes a link to a professional malware removal application to help you remove Cosw and other viruses from your computer.

    After exiting the Registry Editor, it may be a good idea to manually search the following locations for any other potentially dangerous files or subfolders: Using the Windows search field, type in the name of the location you want to open /exactly as it is written below/ and hit Enter.

    1. %AppData%
    2. %LocalAppData%
    3. %ProgramData%
    4. %WinDir%
    5. %Temp%

    Any suspicious-looking files or subfolders that have lately been introduced should be properly examined in each location. To remove any possibly malicious temporary files from your computer, delete everything in the Temp folder.

    After that, look for any malicious changes to the Hosts file on your machine. Opening the Run dialog box (by pressing Windows and R simultaneously) will allow you to access the Hosts file, which you can open by copying and pasting the following command in the Run box and clicking OK:

    notepad %windir%/system32/Drivers/etc/hosts

    Report any instances where the “Localhost” section of the Hosts file contains numerous suspicious IP addresses (like those on the image below). Please let us know in the comments if you detect any more modifications to your Hosts file that could be dangerous.

    How to Decrypt Cosw files

    It is possible to employ a range of decryption methods while dealing with ransomware attacks. Based on the variant of ransomware that has attacked the system, some file-restoration options may not be as effective as others. In order to have a better chance to restore your files, you must first figure out which Ransomware variant you are dealing with. Encrypted files can be searched for specific file extensions attached to the end to acquire this information.

    New Djvu Ransomware

    STOP Djvu is a new Ransomware variant that is posing a global threat to users. If your encrypted files end with the .Cosw extension, you’ve most probably been infected with this particular variant.

    Good news: If this ransomware has used an offline key to encrypt data, victims may be able to decrypt their files. Please use the following link to access a file-decryption tool created specifically for this ransomware version that may potentially help you.


    Click “Run as Administrator” then “Yes” to launch the decryption tool that you’ve downloaded from the link. Please read the license agreement and instructions on your screen before proceeding. The decryption procedure can be started by selecting the Decrypt button. Please note that this program may be unable to decrypt data encrypted using unknown offline or online encryption

    Important! Before attempting to decrypt any encrypted data, please run a full system scan to check for any ransomware-related files or dangerous registry entries. You can eliminate Cosw-related dangerous files from your computer using the recommended anti-virus software and the online virus scanner. If you have any questions, or you find yourself in trouble, please feel free to leave a message in the comments section below this guide.

    About the author

    Violet George

    Violet is an active writer with a passion for all things cyber security. She enjoys helping victims of computer virus infections remove them and successfully deal with the aftermath of the attacks. But most importantly, Violet makes it her priority to spend time educating people on privacy issues and maintaining the safety of their computers. It is her firm belief that by spreading this information, she can empower web users to effectively protect their personal data and their devices from hackers and cybercriminals.

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