Researchers in the Israeli Ben Gurion University have demonstrated an innovative keylogger called “Airhopper”.
It is installed on an absolutely isolated computer, which is disconnected from the Internet.
The keylogger then tricks the computer to transmit its secrets over the display cable. The information is transmitted over an FM radio frequency and can be picked up by a nearby mobile phone.
See this amazing demonstration:
The full research is available on the BGU security labs website.