Virtob virus infects worms that help it spread faster

There’s already a mind-blowing amount of malware floating around the Internet, and the individual worms, viruses, and Trojans are bad enough on their own. When they learn to work in tandem with each other, however, they take the infection game to a whole new level. BitDefender recently noted that in a sample of 10 million infected files, more than 40,000 of them showed signs of a dual infection: files that were compromised by a self-propagating worm that itself had been infected by a virus.

It’s not in a computer virus’ nature to spread itself — it needs help from other software. What BitDefender observed is that one particular virus, Virtob, is actively infecting worms in order to increase its reach. In particular, it has been seen hopping on files that have had malicious code injected by the Rimecud worm — which spreads via file sharing programs like BearShare, DC++, and eMule, USB mass storage devices, and instant messaging applications.

With the Virtob virus in tow, new computers are now double infected and put their users at significantly greater risk. Both pieces of malware receive different instructions from separate command and control servers, and both respond in different ways — Rimecub likes to steal passwords and contact lists, and Virtob prefers to hijack web pages and trick users into installing fake AV software and other crapware.