MMUZ Ransomware (.mmuz File Extension)

What is Mmuz?

Becoming infected with Mmuz ransomware entails severe repercussions. This virus implements a range of system setting modifications that severely hamper usability. Beyond altering settings, the malware encrypts your files, rendering them inaccessible.

Mmuz ransomware employs the Salsa20 encryption algorithm, consistent across the STOP/Djvu ransomware family, to which Mmuz belongs. While decryption tools exist that may restore access to your files without necessitating a ransom, success partially hinges on luck. Files encrypted with an offline key present a substantial chance for recovery. Conversely, files encrypted with an online key are typically irrecoverable.

Preventing ransomware attacks is paramount. Mmuz ransomware often infiltrates systems through software obtained from questionable sources. Despite being freely available, these applications should be legitimately purchased from their respective official websites. Additionally, some programs are crafted for illicit purposes, such as cheating or unauthorized Windows activation. During the process of making these programs freely usable, hackers are at liberty to embed any form of malware, determined by the highest bidder.

Mmuz Encryption process

The Mmuz 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 - ".mmuz". 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 Mmuz 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.

Mmuz 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:

Indicators of Compromise(IOC)