CRT Eavesdropping: Optical Tempest

PortalCell writes "LED status monitors may potentially leak data in a few applications, but worse: Markus Kuhn has now revealed (pdf) that it's possible to read your monitor indirectly just by observing how the blue flicker lights up the room! Forget taping up LEDs or living in a metal box - now you might have to do without sunlight to be secure!" Hopefully people will also stop submitting the LED story now.

LCD monitors and laptops are safer from this

[phr2]

than CRT's. Kuhn's attack works by rapidly sampling the light intensity as the electron gun whizzes around the CRT screen. With LCD's, the light comes from a constantly-on fluorescent tube and there's not the same type of scanning; the LCD itself reacts much more slowly than a CRT does. The optical emanations just don't have as much bandwidth and can't carry all that info. Of course you still might leak screen contents thru RF emissions from the video card, but that's the usual TEMPEST that we already know about. (Note: this info is from Kuhn's paper).

Re:Ridiculous

[wirelessbuzzers]

Did you read the article? If not, please do not post that it is ridiculous. What you didnt notice was that the color you get from such an attack is merged only with the ambient color from the room, which could be filtered out by a simple brightness, contrast calculation. The color from the monitor is not merged because different pixels light up at different times in a CRT.

Please change your sig

[Anonymous Coward]

Some of us are browsing /. from the workplace (sure beats doing actual work) and cannot use a better browser than IE, and I guess it's your sig that widens the page with a windowed IE (I get scrollbars unless I suppress your post). Have mercy on us poor souls, thank you.

Big deal

[t_allardyce]

you can evesdrop on conversations by hiding in a bush and using a gadget to read the vibrations of a window from the reflected light on it.

You can pickup cordless, and maybe even cellphones (digital/encryption though).

You can open up the phone junction box outside the building and tap the wires.

You can pick-up the emf from a monitor or tv and reconstruct the image (pretty hard i think).

You can use the earth wire in a house to transmit data from bugs hidden in plugs.

You can use tools like netbus etc.. to view peoples computer over a network.

You can trick security guards with dumb-busty-blondes(tm)*

*I in no way endorse the use of busty-blondes(tm) or in anyway imply that they are all dumb, or that security guards are shallow/thick and are easily seduced.

You can look into windows with telescopes

You can recover badly deleted data from disks

You can packet sniff

You can abuse the fact that your an admin for that network and get anything you want

You can even use money to get information

And now you can use LEDs and monitor flicker too... And the FBI wants _more_ rights to tap you?!?!? how does that work?

Re:Flat Screens

[Technician]

flourescent high frequency? they still run at 60 Hz
Please research the electronic balast on the compact flourrescent bulbs. They are not a big inductor that the old F40CW bulbs used. After AC is rectified into DC, a high frequency oscilator drives the bulb through a balast capacitor. They operate depending on manufacture in the 6-25 KHZ range. Even the PDF file mentions they are a good source of noise because sevral bulbs are not in sync making the noise harder to predict and remove as a repetative waveform.