Yet another method of remotely eavesdropping on computers has been discovered by boffins in the US.
This time it's done by monitoring the flashes of LED lights on electronics equipment and the indirect glow from monitors.
According to Joe Loughry, the author of a report called Information Leakage from Optical Emanations, optical signals from LED lights can be captured with a telescope and processed to reveal all the data.
Loughry, a computer programmer at Lockheed Martin Space Systems in Denver, said that it requires little apparatus, can be done at a considerable distance, and is completely undetectable.
Loughry claims to have collected a strong optical signal from about 22 yards, using optical sensor equipment. He said that all a hacker had to do was look through the window.
The LED indicators act as little free-space optical data transmitters, like fibre optics but without the fibre.
He said that equipment used in low-speed, long-distance networks typically found in proprietary networks were most at risk.
But he said that it was easy for IT managers to avoid.
All they have to do, Loughry says, is locate equipment away from windows, put black tape over LEDs or de-activate them when not in use.
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