CATEGORY: Emerging Threat
PUBLISH DATE: 19 December, 2018
A second variant of destructive Shamoon V3 wiper has re-emerged after the absence of two years with a more destructive wiping malware (Trojan.Filerase) which will delete and overwrite files on the infected computer, meanwhile the Shamoon itself will erase the master boot record of the computer, making it unusable eventually. The addition of Filerase wiper have made this a more vibrant threat because if the files are erased by the Filerase malware first, they would not be recovered forensically as well.
Filerase is spread across the victim’s network from one initial computer using a list of remote computers. This list is in the form of a text file and is unique to each victim, which indicates that the attackers have likely gathered the information from the earlier reconnaissance phase of the attack. This list is first copied by a component called OCLC.exe and passed on to another tool called Spreader.exe. The Spreader component will then copy Filerase to all the computers listed. It will then simultaneously trigger the Filerase malware on all infected machines.
When the Trojan is executed, it enumerates all the fixed drives on the compromised computer and then deletes all the files and folders on the fixed drives.
For files whose path contains %SystemDrive%\Users or whose path does not contain %SystemDrive% , and whose size is less than 100,000,000 bytes, the Trojan:
Fills the file with random data
Renames the file to a random name
Deletes the file
Erasing Boot record and making the infected computer unusable
Malware Hash (MD5/SHA1/SH256)