Two hacking experts have adapted a laser pen could pick up what you are typing from 100ft away.

Andrea Barisani, chief security engineer at Inverse Path and hacker Daniele Bianco  said that the hack works due to the frequencies of different keys that the pen can detect.

Hackers could establish what you are typing, including addresses, emails or even bank details from online purchases. Dubbed Transmitted Electro-Magnetic Pulse/Energy Standards & Testing (TEMPEST), the beam is aimed directly at the laptop case, generally the LCD display lid.

It works through walls and if an invisible infrared laser is used, the victim would never know. It is also impossible to stop. However security experts said that this will not be the computer security equivalent of the swine flu. Security forces have used something like it for a while, but it has never really caught on.