Cosw Ransomware (.cosw Files)

Cosw Ransomware uses the Salsa20 encryption algorithm. This STOP/Djvu family is one of the most popular infection!

You may be interested in taking a look at our other antivirus tools:
Trojan Killer, Trojan Scanner.

About Cosw Ransomware:

NameCosw Virus
File Extenstion.cosw
Contact[email protected], [email protected]
FamilySTOP/Djvu Ransomware
Offline IDfTU4hYOJ0niv7WAg9utRTzxXv2TcoEvGPJhzIot1
Last seenMarch 12, 2023
AlgorithmSalsa20 encryption. If Cosw cannot establish a connection to crooks server before starting the encryption process, it uses the offline key. This key is the same for all victims(!), making it possible to decrypt .cosw files in the future.
RansomFrom $490 to $980 (in Bitcoins)
  1. โฎž Can delete Volume Shadow copies to make victimโ€™s attempts to restore data impossible;
  2. โฎž Adds a list of domains to HOSTS file to block access to certain security-related sites;
  3. โฎž Installs password-stealing Trojan, like Redline Stealer, Vidar Stealer, Smokeloader, Azorult and others;
DistributionThird-party downloaders, installers, peer-to-peer networks, RDP exploits, etc.,
RSA Public Key-----BEGIN PUBLIC KEY----- MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAwhbzSU/RiBxX4oxDqunU 9VhWvvVRrVdcW+jVpL4otXD4yNHqD7xJLxPsoX6AsIiIio1zjCTeSgyWyswk8ay6 HzHYbhW30qp+g6Z1mz2b2B7KSNY+JX6PNWzdCCEWO1udpQ9M9jbiOg8ws59dnT7i LTeCEWV/uDEAzsBjEwESZn3Qst2n9O3BvfCBak50wLbscyk0sTej37Tc62V8E8X7 I9XY4xDsMkg/n1rYs6E9oAfhq25y2dlAAnyGa8riBgKsUkeOH/tkKfvlT2MAd8OG gPNi8unQY1M2DjGm74SYsX+ecl2AgwPpJuWT5Sbp29PBQH1n0CyJGQ6iJCmV3PXK lQIDAQAB -----END PUBLIC KEY-----
Other variants
  • Goba Ransomware (.goba encrypted files)
  • Goaq Ransomware (.goaq encrypted files)
  • Gosw Ransomware (.gosw encrypted files)
  • Cosw Ransomware (.cosw Files) - What is it? Keep Your Privacy Well

    The appearance of the .cosw files on your computer mean that you are attacked by Cosw ransomware. This malware is targeted at your wallet - it encrypts the files and then asks you to pay the ransom to decrypt them. Before the encryption, it makes several changes in your system to disable any security mechanisms and prevent the launch of antivirus programs.

    Cosw ransomware uses Salsa20 encryption. This cipher is not the most strong encryption but still cannot be decrypted in familiar ways.

    The changes Cosw virus does to the security of your system are pretty heavy. The malware disables the Microsoft Defender and alters some configurations, so you will not launch the installation files of most antivirus tools. It also changes the HOSTS file, leading to an inability to open some of the websites with ransomware removal and file decryption guides.

    Encryption process

    The Cosw ransomware uses the Salsa20 encryption algorithm. That is not the strongest method, but it still provides an overwhelming amount of possible decryption keys. To brute force the 78-digit number of keys, you need 3.5 unvigintillion years (1*10^65), even if you use the most powerful regular PC. Quantum computers can show a bit better results, but it is still too slow to get your files back while you are alive.

    The exact algorithm of encryption is next: malware scans each folder for the files it is able to encrypt. Then, when it finds the target, it makes a copy of your file, removes the original one, encrypts the copy and leaves it instead of the removed original. Such a procedure is done to prevent the situation when you have already opened the file, so ransomware is not able to read it because of the Windows restrictions. To each encrypted copy, the virus adds the specific extension - ".cosw". Then, ransomware creates a _readme.txt file in the folder where the encrypted file is located, and goes to the next folder.

    .COSW Files

    Such an encryption method can be exploited for file recovery. Since the original file is deleted, you may try to recover it using the file recovery tools. The less time is passed - the bigger the chance to get your files back, so hurry up!

    Another specific moment that can help you to use the files even after the encryption is the fact that Cosw ransomware encrypts only the first 150KB of each file. Hence, you can try to run a big file, such as video or music, without the encryption. Similar feature also works with other ransomware families - Dharma, Conti and Makop encrypt the same 150KB.

    Ransom note: _readme.txt

    Ransom note is the same for the whole ransomware family. In fact, it is one of the main signs of to which family the certain ransomware belongs. Here is the typical note for STOP/Djvu family:


    Don't worry, you can return all your files!
    All your files like pictures, databases, documents and other important are encrypted with strongest encryption and unique key.
    The only method of recovering files is to purchase decrypt tool and unique key for you.
    This software will decrypt all your encrypted files.
    What guarantees you have?
    You can send one of your encrypted file from your PC and we decrypt it for free.
    But we can decrypt only 1 file for free. File must not contain valuable information.
    You can get and look video overview decrypt tool:
    Price of private key and decrypt software is $980.
    Discount 50% available if you contact us first 72 hours, that's price for you is $490.
    Please note that you'll never restore your data without payment.
    Check your e-mail "Spam" or "Junk" folder if you don't get answer more than 6 hours.

    To get this software you need write on our e-mail:
    [email protected]

    Reserve e-mail address to contact us:
    [email protected]

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    Indicators of Compromise(IOC)

    File NameMD5File Size
    ๐Ÿ“œ SAMPLE.EXE4dae8b69aab98ab5f96d9db7b8d8d799839168
    ๐Ÿ“œ SAMPLE.EXE3a4f29721c1c8166183a2812dac96e6e838656
    ๐Ÿ“œ SAMPLE.EXE20e8743f652a666da6770e142705e9e5837632
    ๐Ÿ“œ SAMPLE.EXE0e5a32db2bc87f31dbb8b82cb1f01212838656
    ๐Ÿ“œ SAMPLE.EXEd1395a85219ab46bcd45459a5f6cfb4a829952
    ๐Ÿ“œ SAMPLE.EXE011eb4dd82662d8d55e954e29a942095829952
    ๐Ÿ“œ SAMPLE.EXE854439726bdbc1f245bc97da0cc21bac830464
    ๐Ÿ“œ SAMPLE.EXE9324c0b47400cd5fc392a52e57aafd5f830464
    ๐Ÿ“œ SAMPLE.EXE5455cf36a15f21a0f31769c4c4d6655c830464
    ๐Ÿ“œ SAMPLE.EXEe80ec3dc9b00399680eb7396815489ba800256