COZA Ransomware (.coza File Extension)

What is Coza?

Noticing that your files now end with a .coza extension signals an infection with Coza ransomware. This pernicious virus holds your files hostage and demands a ransom, typically around $1000, for their release. However, there are alternative solutions to this dire situation.

Deciphering the encrypted files necessitates specific software, as the Coza virus employs a cipher with 2^256 possible keys. Attempting to crack this encryption manually, even using brute force, would be futile, consuming more time than the Earth's estimated lifespan. In contrast, dedicated decryption tools can achieve this in just an hour.

Restoring your system's settings, which ransomware alters to compromise security, requires additional tools. These modifications, aimed at weakening your defenses, must be reversed to ensure functionality and access to various online resources. GridinSoft Anti-Malware aids in this recovery while removing the ransomware.

The mode of virus transmission is also crucial to understand. The Coza ransomware, belonging to the widespread STOP/Djvu family, primarily spreads through software obtained from unreliable sources. Websites like eMule or ThePirateBay are often used to download applications for free. Unfortunately, in the process of making these programs usable without purchase, hackers can insert any form of malware, including Coza ransomware.

Coza Encryption process

The Coza 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 - ".coza". Then, ransomware creates a _readme.txt file in the folder where the encrypted file is located, and goes to the next folder.

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 Coza 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.

Coza note:

Ransom note is the same for the whole STOP/DJVU 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:

External Links:

Indicators of Compromise(IOC)