Security researchers found that poor shielding on some keyboard cables means useful data can be leaked about each character typed.

By analysing the information leaking onto power circuits, the researchers could see what a target was typing.

The attack has been demonstrated to work at a distance of up to 15m, but refinement may mean it could work over much longer distances.

Hotel attack

"Our goal is to show that information leaks in the most unexpected ways and can be retrieved," wrote Andrea Barisani and Daniele Bianco, of security firm Inverse Path, in a paper describing their work.

The research focused on the cables used to connect PS/2 keyboards to desktop PCs.

Usefully, said the pair, the six wires inside a PS/2 cable are typically "close to each other and poorly shielded". This means that information travelling along the data wire, when a key is pressed, leaks onto the earth wire in the same cable. read on