Earlier this week, security firm Panda Labs reported that it had discovered that 25 percent of newly created worms have been specifically designed to spread through USB storage devices. Nowadays, this means not just USB flash drives, but any device that can be attached to a computer and used as external storage, including digital cameras, external hard drives, media players, and smartphones.

It's a simple enough technique: when an external storage device is attached to a Windows PC, if the root directory of the device contains an autorun.inf file, Windows will take the actions specified in the file. Naturally, if hackers have modified the autorun.inf file, it can be used to run any malware on the drive, causing the computer to be infected.

Email and the Web are still the most popular methods of malware transmission, but things are rapidly changing as more devices can be attached to PCs and emulate a dedicated external drive.

Spotted here