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LED Lights: Friend or Foe?

Posted by michael on from the brilliant-deductions dept.

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!"

4 of 597 comments (clear)

  1. I call BS on this one... by MentlFlos · · Score: 1, Troll
    Ok, First off LED's as a status indicator just blink when there is activity. For example, a packet has been sent or received. Now how many variations can one packet have? I'm not even going to try to figure it out.

    I can only think of one way this can happen. If someone wires up the LED's so that they are hooked directly to the transmit and receive wires so they do actually blink out the bits. Then one would need to send data slow enough so the LED (and receiver) can make out the individual pulses. In this respect, stupid=yes, impossible=no.

    Or like usual, I could be just blowing smoke out my ass...

  2. There must be meaning behind this maddness by Simpler · · Score: 0, Troll
    Let's do a quick calculation to see if this is feasible.

    Let's assume you've got a slow connection on your average modem and you're running your dialup at 33Kps. This means that you're looking at having that blinking light going through on-off cycles every 1/33000 of a second if you can read the data accurately.

    Considering the quality of your average LED inside the modem, I'd be amazed if they can blink on-off distinctly more than 100 times a second. Anything faster else would blur.

    .... and what do you do with an invalid checksum on the IP packet? Phone the guy's house up and ask them to resend the packet?

    This conspiracy theorist should concentrate on finding meaning in radio waves from space.

  3. THIS IS FAKE by Gordonjcp · · Score: 0, Troll

    I've looked at many, many modems. Almost all of them have the LED driven by an IO pin on the microcontroller inside them. Assuming the anode of the LED is connected to +5v, and the cathode to the IO pin (this is pretty standard - the pins can sink more current than they can source), the IO pin is pulled low when the controller is in its interrupt handler, talking to the UART.

    I have got an extremely old 300-baud modem and a 1200-baud modem, which have the LED's connected to the data lines. It would work on those, but not on most modern modems.

    Sorry, but this paper is a complete hoax. Based in truth, but only loosely now.

    Panic over folks, peel that sticky tape of your modems and enjoy "das blinkenlichts".

  4. Bull SHIT by Guitarman · · Score: 0, Troll

    no way in hell can they do that, it's incredible that such crap can be taken seriously.