Most computer users have probably found themselves at the wrong end of a malware-infected USB flash drive at least once. In fact, as US Deputy Defense Secretary William J. Lynn III recently revealed, even the mighty US military has firsthand experience of the damage a rogue USB flash drive can cause. Their ubiquity has made portable storage devices the ideal carriers for computer worms. But how popular exactly are they among malware authors? Panda Security's research arm PandaLabs claims to possess the answer.

The security company estimates that a quarter of all new worms use portable storage devices to spread themselves. It arrived at such a high estimate after surveying more than 10,000 small and medium firms. "Much of the malware in circulation has been designed to distribute through these devices," said Luis Corrons, the technical director of PandaLabs, in a statement. "Not only does it copy itself to these gadgets, but it also runs automatically when a USB device is connected to a computer, infecting the system practically transparently to the user."