Gujd Virus Ransomware (.gujd File)

What is Gujd ransomware?

Ransomware has a lot of faces. In the case of Gujd ransomware, it is a virus that targets individual users and, like any other ransomware, encrypts the files it can reach on the infected computer. In addition, it disables your security tools and makes networking quite hard.

The files it encrypts are very hard to get back. Malware uses a robust encryption algorithm - Salsa20, which is likely impossible to hack with brute force. Then, the virus sends the decryption keys to its command server, which is controlled by cybercriminals. Those guys will give you the decryption key only after the ransom payment or after being captured by the police.

Gujd ransomware is distributed through pretty standard channels, used by various other viruses. “Free” software, which you can get through the peering networks (eMule, ThePirateBay), is a perfect shell for ransomware because the user will likely ignore all alerts from the security systems. After the attack, they will not even see any signs of life from the antivirus program.

Encryption process

The Gujd 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 - ".gujd". 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 Gujd 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:

Indicators of Compromise(IOC)

File Name	MD5	File Size
📜 SAMPLE.EXE	69b3713712704f1002c43a39ce7eb629	726016