Researchers in Switzerland have proved that it is possible to identify keystrokes made on a wired keyboard by tracking electromagnetic emissions.

In a paper for the Lausanne Security and Cryptography Laboratory researchers Martin Vuagnoux and Sylvain Pasini demonstrated that certain keyboards, particularly modern ones, contain enough electronic components to reveal what is being typed from a distance.

"We conclude that wired computer keyboards sold in the stores generate compromising emanations (mainly because of the cost pressures in the design)," they said.

"Hence they are not safe to transmit sensitive information. No doubt our attacks can be significantly improved, since we used relatively inexpensive equipment."

The team has posted video of keystrokes being recorded from a distance of one metre using a simple wireless aerial. Software developed by Vuagnoux then converts the signals into accurate text.

The method is similar to a technique known as Van Eck phreaking developed by Dutch researcher Wim van Eck in 1985 to spy on computer monitors from a distance.