LED Lights: Friend or Foe?

elfdump writes: "In an article (pdf) soon to be published in ACM Transactions on Information and Systems Security, security researchers have discovered that data transmitted through modems and routers can be remotely reconstructed from the equipment's LED status indicators. According to experiments, their light-to-information retrieval method is successful even when the light is captured 'at a considerable distance' from the source. If you want to prevent people from spying on your data, you may want to tape up those blinking LEDs!"

Comments

Tempest

[Bruce Perens]

Look around for info on the U.S. government's declassified Tempest program. That shows how you can really do this, by sampling the radio emissions of the equipment. Any rapid switching creates radio waves, if you don't shield them effectively you may indeed leak information off site. There have been demonstrations of reading a CRT by the video monitors radio emissions.

To do this with an LED would require that the LED be actually driven by the data signal. Most of them go on at the start of the packet or byte and go off at the end, they don't go on for 1 and off for 0. So, you might be able to do a little traffic analysis, but you would not be able to recover the data.

Bruce

Re:Tempest

[fsmunoz]

Look around for info on the U.S. government's declassified Tempest program. That shows how you can really do this, by sampling the radio emissions of the equipment. Any rapid switching creates radio waves, if you don't shield them effectively you may indeed leak information off site. There have been demonstrations of reading a CRT by the video monitors radio emissions

Indeed. Here is a program that implements just that. Tempest for Eliza is an interisting program... it actually played classical music on my AM radio using the monitor color intensity! There's a mod for mp3 even. Check it out.

cheers,

fsm