Have you considered that someone could be reading what's on your monitor from a few rooms away? It's unlikely, but possible, as work by Cambridge University computer security researcher Markus Kuhn shows.
Back in 1985, Wim Van Eck proved it was possible to tune into the radio emissions produced by electromagentic coils in a CRT display and then reconstruct the image. The practice became known as Van Eck Phreaking, and NATO spent a fortune making its systems invulnerable to it.
CRTs are now well on the way to being history. But Kuhn has shown that eavesdropping is possible on flat panel displays too. It works slightly differently. With a flat panel display the aim is to tune into the radio emissions produced by the cables sending a signal to the monitor. The on-screen image is fed through the cable one pixel at a time. Because they come through in order you just have to stack them up. And Kuhn has worked out how to decode the colour of each pixel from its particular wave form.
If everything is just right, you can pick up signals from some distance. "I was able to eavesdrop certain laptops through three walls," says Kuhn. "At the CEBIT conference, in 2006, I was able to see the Powerpoint presentation from a stand 25 metres away."
via New Scientist
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