Flickering Computer Lights Could Pose Threat To Privacy

Ananova ^ | 3-7-2002

[blam]

Flickering computer lights could pose threat to privacy

New research suggests it may be possible to eavesdrop on computers just by watching the flicker of LED lights.

US scientists believe it's possible to correlate the flash of light emitting diodes with the data being processed.

They say it could mean many millions of devices are vulnerable.

The research is titled Information Leakage from Optical Emanations. It has been co-authored by researchers at Lockheed Martin Space Systems in Denver and Auburn University in Alabama.

The work suggests software-controlled LEDs can carry a modulated optical signal that echoes the flow of data.

This means attackers could gain access to classified or personal data just by watching and de-coding the flickering light. No physical access to the machine being watched is required.

The paper says deciphering the flashes "requires little apparatus, can be done at a considerable distance, and is completely undetectable".

Authors Joe Lughry and David Umphress add that LED indicators are present on many millions of communications devices, including modems, routers and even keyboards.

According to the Zem website - which logs cryptology research - the paper is due for publication later this year.

Story filed: 10:52 Thursday 7th March 2002

[blam]

Where are the LED'S mentioned located on my computer? Will someone explain this further?

[general_re]

There was a Slashdot thread about this yesterday. What they're talking about are the LED's that you see on exernal modems and the LED's that are found on Ethernet cards, on the back of your machine. External cable and DSL modems tend to have them as well.

[Physicist]

Relaxen und watchen das Blinkenlights.

[DouglasKC]

I was in the Air Force 1982-1986 and worked on top secret computer equipment. We had a demonstration one day about how easy it is to decipher the RF radiation from non shielded computers or any other electronic device to eavesdrop.

If you're worried that spies have built and/or purchased sophisticated equipment to spy on you then you can thwart them by increasing the shielding on your pc by putting it in a metal shielded enclosure.

[general_re]

exernal = external

[Izzy Dunne]

The work suggests software-controlled LEDs can carry a modulated optical signal that echoes the flow of data.

News to me...
If there's an LED on your disk drive - it just means that access is happening, I doubt it flashes according to the ones and zeroes of your data.
There's an LED in my mouse - used to see how far I move it.
There's several LEDs on my network hub - just to indicate activity. I doubt they indicate content, since the average brightness doesn't vary.
There's a power LED on my speaker box.
There's a power LED on my monitor.

[general_re]

Now there's one I haven't seen in a good long time. But it's not fair to whet people's appetites and then not give over the whole thing ;)

ACHTUNG! ALLES LOOKENSPEEPERS!

Das computermachine ist nicht fuer gefingerpoken und mittengrabben. Ist easy schnappen der springenwerk, blowenfusen und poppencorken mit spitzensparken. Ist nicht fuer gewerken bei das dumpkopfen. Das rubbernecken sichtseeren keepen das cotten-pickenen hans in das pockets muss; relaxen und watchen das blinkenlichten.

[sigSEGV]

That was my initial impression. However, even a solidly LED will transmit information due to the slight loss of power for every bit transmitted. The flickering is much quicker than the human eye see.

[Rodney King]

So put a piece of tape over it.

[general_re]

I haven't read it, but here's the article (PDF) about this that's apparently going to be published in one of the ACM journals...

[MrB]

I really don't believe that an LED can "react" fast enough to reflect every bit being transferred.
One thing that would lay this technical conundrum to rest - Are the LEDs used in fiber-optic transmitters the same type/speed as those used to indicate network activity?

If those are the same, then the "reaction time" would have to be fast enough to reflect data transfer rates.

[general_re]

Funny you mention that - I'm just skimming the article, and there's this bit:

LEDs are very fast; that is, they exhibit a quick response to changes in the applied drive voltage (tens of nanoseconds). In fact, common visible LEDs are fast enough that a close cousin is used as a transmitter in fiber optic data links at speeds in excess of 100 Mbits/s [Hewlett-Packard Company 1993b].

Although fast response time is oftentimes a desirable quality in a display, LEDs are fast enough to follow the individual bit transitions of a serial data transmission.

[sigSEGV]

Apparently, an LED will react quickly enough to decipher information up to 10Mhz.

[sigSEGV]

I'm not an electrical guy, but wouldn't putting a small capacitor on each LED "smooth out" the flickering and make it safe?

[general_re]

If you have the article handy, on the bottom of page 9, they say that they weren't able to recover data from any of the network cards they tested. This is apparently because network cards use a pulse-stretching circuit to make the visible flashes longer, and thus more easily seen by humans. This also has the effect of making it impossible to recover the data stream from the light pulses - if you did something like that in all devices, if would presumably have the same effect.

[Nick Danger]

[blam]

"I'm not an electrical guy, but wouldn't putting a small capacitor on each LED "smooth out" the flickering and make it safe?"

I'm a retired chip-maker of thirty years (process), 'draw it up', it can be made.

[Politically Correct]

And don't forget the IR led that many computers and laptops now have.......what's it doing right now?

[Free the USA]

Check the Bump List folders for articles related to the above topic(s) or for other topics of interest.

[2OOOll]

relaxen und watchen das blinkenlichten

Wenn Sie haben keinen blinkenlichten anzündet der Nadel des Meters zuschaut.