Scientists in Germany have demonstrated a startling new form of surveillance: identifying people using nothing more than ordinary WiFi signals. By analyzing how radio waves bounce around a room, researchers can effectively “see” and recognize individuals — even if they are not carrying a device and even if their phone is turned off.
Faraday cage, it’s going to be a hassle to wiremesh your entire apartment, and you can forget using a mobile phone inside of it, but there are no outside signals getting in that way.