The Month: New threat to businesses emerges

The name comes from the method the devices use to transmit the stolen data in "jittery" chunks by adding a tiny processing delay after a keystroke.

A US graduate student, Gaurav Shah, built a version using simple components.

"This is spy stuff," Shah told reporters. "Someone would need physical access to your keyboard to place a JitterBug device, but it could be quite easy to hide such a bug in plain sight among cables, or replace a keyboard with a bugged version."

"Although we do not have evidence that anyone has actually been using JitterBugs, our message is that if we were able to build one, so could other, less scrupulous people," he added.