A rare example of a destructive computer worm has been spotted on the web.
Zimuse-A and its variant, Zimuse-B, overwrite MBR (Master Boot Record) files on infected drives with their own data, either 40 days or 20 days respectively after infection. This malicious behaviour corrupts records and makes data recovery difficult if not impossible, anti-virus firm Eset reports.
Eset cites circumstantial evidence suggesting the worm was originally created as a prank, targeting bikers in central Slovakian region of Liptov. One of the worm's infection routines attempts to trick users into clicking a pop-up box that informs them of supposed problems with the www.offroad-lm.szm.sk site.
Whether the worm was original created to hit users of that group or not, it has now spread far and wide.
Eset said it has detected hundreds of incidents of infection since the malware started spreading. After first cropping up in Slovakia, the malware has spread to the US, Thailand and Spain. The worm is distinct from most of the malware currently in circulation, much of which either attempts to drop a backdoor on compromised systems, turn them into botnet clients, or both.
Zimuse-A and its variant most closely resemble ransomware Trojans, but unlike them they mess with records, potentially corrupting data on compromised systems, instead of making any intent to encrypt data.
The worm spreads via malicious content hidden on legitimate websites, sometimes disguised as an IQ test. It can also spread via infected USB drives, a technique that has become the malware's primary method of infection.
More about the malware and speculation about its possible origins and purpose can be found in a blog entry by Eset here. ®