Reflected Wi-Fi signals allow snoopers to read text through walls

Wi-Fi signals can see through walls, revealing images of still objects and even making it possible to read 3D text. The technique could have security applications, but there are also risks to people’s privacy.

Using Wi-Fi signals to snoop isn’t a new idea, but until now tools that do this have relied on movement: one recent experiment that used three transmitters and three receivers in a room could detect the shape of people’s bodies …