Viruses

Foza Ransomware is a devastating encryption virus from the series of STOP Ransomware (Djvu Ransomware). Foza Ransomware is a variant of the STOP/Djvu Ransomware family, which is known for using a combination of two encryption algorithms: RSA and AES. RSA is used to encrypt the symmetric AES key that is generated for each file. This means that each file has its own unique AES key, which is used to encrypt and decrypt the file's contents. The RSA key pair is generated by the ransomware on the victim's computer and the public key is sent to the attacker's server, which is then used to encrypt the symmetric AES key. It has got its name from .foza extension, that ransomware adds to the end of encrypted files. From a technical point of view, the virus remains the same as previous versions. Only thing that changes during past couple of years is contact details of malefactors.

Kafan is a new ransomware virus that infects Windows users in order to encrypt personal data and extort money for its decryption from victims. Once installed, the ransomware will run a quick scan of the stored data and start the encryption process using strong cryptographic algorithms. In addition, the malware will also assign its own .kafan extension to distinguish locked files. For instance, a file originally named 1.pdf will change to 1.pdf.kafan and become no longer accessible. Lastly, the file encryptor generates a ransom note called help_you.txt with instructions on how to return the data. The ransom message necessitates victims to send an e-mail message to cybercriminals (PYTHONHAVENONAME@163.COM) and pay for decryption. While sending the message, victims are also asked to write their ID in the message title/subject. The price for decryption is said to depend on how fast victims establish communication with the attackers. Cybercriminals employ such manipulation techniques to put extra pressure on victims and potentially force them into agreeing to pay the ransom.

Recov is a new ransomware variant of the VoidCrypt family. After infiltrating a system, it runs data encryption (to prevent victims from accessing files) and tells victims to pay for a kit of decryption software + RSA key for unlocking the files. Instructions on how to do it are presented inside the Dectryption-guide.txt ransom note. One more thing that this ransomware does is assigning visual changes to encrypted files - a string of characters consisting of the victim's ID, cybercriminals' e-mail address, and the .Recov extension will be added to filenames. For instance, a file originally named 1.pdf will be changed to 1.pdf.[MJ-TN2069418375](Recoverifiles@gmail.com).Recov or similarly. Cybercriminals demand that victims establish contact with them via e-mail (Recoverifiles@gmail.com or Recoverifiles@protonmail.com in case of no answer). While it isn't made clear what extortionists need, it is likely that they will require their victims to pay a certain fee for a decryption tool and RSA key that are available only to the developers.

Kadavro Vector is a ransomware program oriented toward English, Russian, and Norwegian-speaking users. The purpose of this virus is to encrypt potentially important data and extort money from victims for its decryption. While rendering files inaccessible, the malware also appends the .vector_ extension to targeted files. For instance, a file originally named 1.pdf will experience a change to 1.pdf.vector_ and reset its original icon. Very soon after successful encryption, Kadavro Vector force-opens its pop-up window containing decryption guidelines. Additionally, desktop wallpapers get changed as well. The ransom note instructs victims to not turn off the Internet and their computer as it may otherwise lead to damage to encrypted data. To return the data, victims have to purchase Monero (XMR) cryptocurrency worth $250 and send it to the cybercriminals' crypto address. In addition, there is also a timer indicating how much time users have to pay for decryption. Should victims not manage to do so within the allocated time frame, it is said that all files will be deleted using high-edge algorithms, making them permanently unrecoverable in the future. By doing so, threat actors try to put extra pressure on victims and thereby force them to meet the decryption demands.

Coty Ransomware is a part of a large STOP/Djvu Ransomware family. It got its name because the original versions of the malware added the .stop (later .djvu) file extension and encrypted them with a combination of AES and RSA cryptography to make files inaccessible on the infected Windows computer. Coty Ransomware according to its name adds .coty extension. This version appeared in the end of April 2023. Once the Coty/STOP ransomware completes the encryption procedure, the virus creates a ransom note to _readme.txt file. The message of the scammers says that the victims must pay the ransom within 72 hours. The authors of the STOP virus are demanding $490 during the first three days and $980 after this time period. To provide confirmation, hackers allow 1-3 "not very large" files to be sent for free decryption to support@freshmail.top or datarestorehelp@airmail.cc for a test.

Cooper is a ransomware virus that infects systems to encrypt potentially important files and demands money for their decryption. Along with running secure encryption, it also assigns the .cooper extension to affected files. For instance, a file originally named 1.pdf will change to 1.pdf.cooper and lose its original icon. After this change, files will no longer be usable, even if you remove the added extension. To reverse these changes, decryption instructions are presented within the Cooper_Recover.txt file. Cybercriminals urge victims to contact them via e-mail and pay for unique decryption software. Threat actors are the only figures who have access to it, and it is said no other tool is able to provide decryption for enciphered .cooper files. While contacting, victims are also asked to include the ID in the subject line of an e-mail message. Unfortunately, unless you have an available backup that can be used to retrieve copies of encrypted files, paying the ransom to cyber-crooks might be the only way to return back your files. Multiple ransomware infections use strong encryption algorithms and generate online keys, ensuring decryption is barely possible without the help of initial developers.

Coza is a new ransomware sample developed by the notorious STOP/Djvu group of extortionists. Alike many other variants published by these cybercriminals, this one employs an almost identical encryption and extortion pattern. Upon settling down on an infected machine, the virus starts scanning and therefore encrypting potentially important pieces of data. By doing so, the virus aims to create more incentives for victims to pay for decryption proposed by the attackers. In addition to encryption, the malware also makes sure victims can differentiate locked from non-locked files – by simply assigning the .coza extension. For instance, a file previously named 1.xlsx will change to 1.xlsx.coza, 1.pdf to 1.pdf.coza and so forth with other targeted file types. To undo the encryption, victims are said to follow instructions within the _readme.txt text note.

Pwpdvl is a ransomware virus designed to extort money from victims by running encryption of data. In other words, people affected by this malware will no longer be able to access and view their files. When Pwpdvl enciphers potentially important files, it also assigns the victim's ID, along with the .pwpdvl extension at the end. For instance, a file like 1.pdf will alter to something like 1.pdf.[ID-9ECFA84E].pwpdvl and rest its original icon. To make victims pay money for the recovery, the file encryptor creates a ransom text note (RESTORE_FILES_INFO.txt), which contains decryption instructions. It is demanded of victims to contact the swindlers (via Bitmessage or qTOX) and pay for decryption in Monero (XMR) cryptocurrency. Before sending the payment, cybercriminals also offer to test free decryption – victims can send 2 encrypted files (non-important and 1 MB max) and get it unlocked for free. This is a kind of guarantee that extortionists offer to prove their decryption abilities and give extra confidence for paying the ransom. Though, please note that trusting cybercriminals is always a risk. Some users get fooled and do not receive the promised decryption tools/keys regardless of meeting the demands. Despite this, it is unfortunately only ransomware developers who hold the necessary decryption keys for safely restoring access to data. Independent decryption using third-party tools or Windows shadow copies can be possible but in very rare cases when ransomware contains flaws or did not manage to encrypt the data as intended.