USB sticks have long been a mechanism for delivering malware to unsuspecting computer users. A booby-trapped flash drive, for instance, was the means by which the US and Israel reportedly infected Iran's Natanz uranium enrichment facility with the Stuxnet worm. And, in case anyone thought USB stick attacks had lost their novelty, last year's Bad USB proof-of-concept exploit delivered a highly programmable attack platform that can't be detected by today's defenses.

Now, a researcher who goes by the name Dark Purple has created a USB device that can permanently destroy much of a computer's innards, rendering the machine little more than an expensive doorstop. Within seconds of being plugged in, the USB stick delivers a negative 220-volt electric surge into the USB port. As the video below demonstrates, that's enough to permanently damage the IBM Thinkpad receiving the charge.

As viewers can see, the USB stick looks normal, and there are no outward signs it's malicious. But the USB Killer 2.0, as its creator calls it, takes computer attacks on a less-traveled road that leads to physical destruction. According to this post from The Daily Mail, an earlier and less powerful version of the device drew power from USB ports using a DC-to-DC converter until it reached negative 100 volts. At that point, the power was directed into the computer. The process ran on a loop until the circuitry failed. It's likely Version 2 works similarly.

It's not clear from Dark Purple's blog post precisely how far the damage from the updated device extends. Presumably the USB port is fried, and it wouldn't be surprising if circuits on the motherboard were damaged, too. The hard drive and CPU, on the other hand, have a better chance of surviving, although that's not clear from the demo, either. In any event, the video is one more reason to be wary of USB devices, especially those that come from unknown sources.