Swiss researchers have demonstrated a way to read anything you type on your keyboard from up to 20 meters away by recording the electromagnetic radiation generated when you press a key.
We found 4 different ways (including the Kuhn attack) to fully or partially recover keystrokes from wired keyboards at a distance up to 20 meters, even through walls. We tested 11 different wired keyboard models bought between 2001 and 2008 (PS/2, USB and laptop). They are all vulnerable to at least one of our 4 attacks.
We conclude that wired computer keyboards sold in the stores generate compromising emanations (mainly because of the cost pressures in the design). Hence they are not safe to transmit sensitive information. No doubt that our attacks can be significantly improved, since we used relatively unexpensive equipments.
If you combine this with this method that can be used to view the image on a CRT monitor from just the reflection it generates on a wall, or another method that lets you view images on any screen when they are reflected off nearly any surface, you have enough reasons never to feel safe again when using your computer. Here are some videos detailing the method used: