Your WiFi router can allow others to "see" what happens inside your house through the walls

The principle of radar is based on the analysis of wave reflection that occurs when you hit these with physical objects in its path. Two researchers from University College London have developed a detector that is capable of analyzing small changes in frequency (Doppler effect) that occur when the waves emitted by a WiFi router crash into objects.

With this information it can detect moving objects, like a human body, and know where it is located behind a wall, its direction and speed. Research is the basis for the development of devices that may be used by the security forces to show the movement of people inside buildings. Moreover, as acts passively using existing WiFi signals, it is undetectable.

www.popsci.com/technology/article/2012-0 eless-router ...