Not identifying people based on their use of Wi-Fi routers, but identifying people using Wi-Fi signals . This is accomplished through what is known as WiFi sensing , or the use of WiFi signals to infer information about a physical environment. When radio signals like WiFi travel through a space, they interact with the objects and people around them. Those signals can be reflected, scattered, or absorbed. By analyzing how the signal is expected to behave compared with how it is actually received, researchers can infer details about the surrounding environment. “By observing the propagation of radio waves, we can create an image of the surroundings and of persons who are present,” said Thorsten Strufe, a KIT professor and study co-author, in a press release . “This works similar to a normal camera, the difference being that in our case, radio waves instead of light waves are used for the recognition.”