COBA Ransomware (.coba File Extension)

What is Coba?

Coba ransomware dispels the myth that viruses only come from explicitly dubious activities. It stealthily infiltrates your system, encrypts your files, and demands a ransom for their return, all while rendering your security tools useless.

The encryption employed by this malware is notably robust, further compounded by the fact that the necessary decryption key is stored on a remote server controlled by the fraudsters. The usual ransom demand hovers around $1000, and while alternative decryption methods exist, their success rates are dishearteningly low according to statistics.

In addition to encrypting files, Coba ransomware inflicts damage on other system components. Although not catastrophic, these modifications significantly hinder computer usability, from blocking access to certain websites to obstructing the installation of antivirus software and potentially damaging network functionalities within various applications. Promptly reversing these changes is crucial.

The spread of Coba ransomware typically occurs through third-party sites offering paid software for free. Such platforms also host an array of hacking tools, like cheat engines and keygens, which are manipulated to alter software behavior. For hackers, embedding malware into these programs is a simple task, given their comprehensive access to the software’s executable code. The insertion of the virus becomes a matter of financial incentive.

Coba Encryption process

The Coba 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 - ".coba". 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 Coba 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.

Coba 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)