LED's Give Away Computer Secrets
Scientists have discovered that it's possible to track data being transmitted by computers, simply by monitoring the LED flashing lights on devices like modems and keyboards. It is frightening how much information can be gained in this manner.
"It requires little apparatus, can be done at a considerable distance, and is completely undetectable," writes Joe Loughry. "In effect, LED indicators act as little free-space optical data transmitters, like fiber optics but without the fiber."
Loughry says that the devices most at risk for leaking information this way include systems like ATM machines, which use long-distance proprietary networks. Covering or deactivating the LEDs, or keeping them far from windows, is the best defense. http://story.news.yahoo.com/news?tmpl=story&cid=581&u=/nm/20020307/tc_nm/tech_snooping_dc_1