The computers' hard drive can be used as a microphone, allowing intruders to listen to the conversations between people around the device.

To demonstrate how to turn a computer hard drive into a microphone, Connor Bolton and his colleagues at the University of Michigan, USA, used the feedback system that helps position the read head above the magnetic disk.

When the read head is struck by sound waves, the mechanical vibrations interfere with the voltage signal produced by the drive position sensors.

By monitoring this signal, Bolton was able to make high quality recordings of people talking near the computer.

According to the team, malicious software can use this technique to record audio and then secretly send it to a remote site, invading a home or office without having to go in there to plant a microphone spy.

[link to spqr.eecs.umich.edu (secure)]