It’s been known for a while that CRT monitors leak radiation which makes them easily duplicable on an external monitor, leading to insane amounts of shielding.

Now it’s the LCD’s turn.

Using a radio antenna and reciever, Markus Kuhn can duplicate your LCD on an external monitor, in some cases though up to three walls away, depending on the type of monitor. Thankfully, it’s fairly easy to defend against.

He’s also found a way to reconstruct what a monitor is showing by looking at the flicker reflected through a window or on a wall.

Markus Kuhn has a few other interesting articles on his own site.