Because there isn’t enough invasion of privacy in our world, Wi-Fi signals can also spy on you: When a router communicates with a device, it gathers information about how the signals travel, which may then be used to identify humans from the way their bodies absorb or reflect the waves, writes Kaveh Waddell for The Atlantic. A number of experiments showed routers could identify someone from the shape of their body or the way they walk. “A pair of MIT researchers wrote in 2013 that they could use a router to detect the number of humans in a room and identify some basic arm gestures, even through a wall.

They could tell how many people were in a room from behind a solid wooden door, a 6-inch hollow wall supported by steel beams, or an 8-inch concrete wall—and detect messages drawn in the air from a distance of five meters (but still in another room) with 100 percent accuracy.” Another system called “WiKey” can tell what someone is typing by monitoring finger movements using only a router and codes created by researchers. Another technology can identify what someone is saying by analyzing distortions and reflections in signals when the mouth moves. Relax, this is not happening just yet: the lead researcher behind WiKey, Kamran Ali, said it only works in controlled environments and with a lot of training. “But as wi-fi “vision” evolves, it may become more adaptable and need less training,” writes Waddell. Let alone the possibility of hacking.