Autorun infections re-emerging in the wild

New attacks are spreading Trojans by way of removable drives

A malware outbreak is using a new twist on an old infection tactic, security experts have warned.

McAfee researcher Vinooo Thomas said in a blog post that the company had seen a rise in the number of malware attacks spreading by way of removable drives.

Many of the attacks take advantage of autorun, a feature in Windows that allows disks and removable media such as USB thumb drives to automatically load content when inserted into a system.

The feature can be disabled, and Microsoft recently released an update for Windows which allows users to set autorun permissions for each drive to prevent devices automatically launching code.

The exploitation of the feature has become a potent way for malware writers to spread infections. Many target thumb drives and other removable media by directing the Trojan to infect the target system, and to reinstall itself on any removable drives along with a specially crafted autorun file.

The infected drive can then either spread the malware to a new host, or reinstall itself on a recently cleaned system.

The tactic brings back memories of some of the earliest computer viruses which, in the days before the internet, spread by infecting floppy disks shared over multiple systems.

"During the past couple of years we have seen malware authors increasingly incorporate the autorun.inf infection vector into malware families, with stunning success," Thomas wrote.

"While the autorun functionality in operating systems does provide some convenience (it saves a couple of clicks), it has single handedly revived the 1980s model of hand-carried malware propagation."