Researchers have uncovered a new variant of the Crysis/Dharma ransomware that appends the .cobra extension to encrypted files. Bleeping Computer credited ID-Ransomware’s Michael Gillespie and Jakub Kroustek with discovering the Cobra Crysis ransomware. The pair then uploaded the variant to the ID-Ransomware site to speed ransomware protection against it.
While it’s still unknown exactly how this variant is being transmitted, in the past, cybercriminals spread Crysis by gaining access to Remote Desktop Services and then manually installing ransomware.
How Cobra Crysis Works
Cobra Crysis encrypts both mapped network drives and unmapped network shares. To guard against this ransomware, businesses should restrict access to network resources to only those who need it.
When the variant encrypts a computer, it deletes all the shadow volume copies to prevent users from restoring data. It then creates two ransom notes. The first note (info.hta) is launched by the autorun feature when a user logs in, while the other (Files encrypted!!.txt) appears on the desktop. The notes instruct users to contact an email address to receive payment instructions, promising to decrypt up to five files for free. Payment of the ransom would assumedly prompt decryption of all the user’s files.
Because the malware automatically runs each time Windows starts up, files added since the encryption originally ran will also be encrypted when the computer launches. There currently isn’t a tool available to decrypt .cobra files for free.
Enhancing Ransomware Protection
To strengthen security in the face of this new threat, businesses should test their backup plans to ensure their reliability. Enterprises should also educate users not to open any attachments from unknown sources and to scan all attachments. Investing in security software that contains behavioral detection will also help to prevent users from falling prey to ransomware threats.