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.
Knowing how.
All routers are just Linux computers managing slightly better than average network cards. (Home routers, obviously. Beefy carrier hardware is different).
A basic setup is essentially installing Linux and then running a handful of commands for packet forwarding. The figuring out how to do it without wifi crashing will take longer because that software is wonky.