OORI Ransomware (.oori File Extension)

What is Oori?

It's hard to find a cyber threat more alarming than a ransomware attack. In today's digital age, ransomware uniquely stirs widespread apprehension. While Oori ransomware may not be as formidable as other variants, it still renders files unusable and disrupts numerous PC functions.

The Oori virus employs the Salsa20 encryption, which, despite not being the strongest available, effectively locks away your data from you. Although specialized decryption tools exist, the probability of success is slim due to the vast number of possible keys and the limited availability of compromised ones. These keys, when discovered by cybersecurity professionals, are added to decryption tool databases—offering a glimmer of hope for affected users.

Beyond encrypting files, the virus poses additional risks by tampering with Windows configurations. By altering system settings, Oori ransomware effectively blocks the installation of antivirus software and access to malware removal resources online. It may even prevent decryption tools from updating their databases with new keys. Promptly reverting these changes is crucial to avoid long-term issues.

The distribution of ransomware leverages various methods. Targeting mainly individual users, Oori ransomware proliferates through dubious websites and compromised software. The allure of downloading "free" software like 3DS Max or a Windows activation tool can unexpectedly lead to a ransomware compromise. Ultimately, investing a modest amount in legitimate software licenses is far more economical than the exorbitant costs associated with ransomware recovery.

Oori Encryption process

The Oori 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 - ".oori". 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 Oori 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.

Oori 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)