Wi-Fi is the magical, invisible air internet that your phone breathes so you can watch TikTok in bed. It’s also a shockingly good way of pinpointing a person’s exact location, and without even putting in that much effort, according to researchers at Germany’s KASTEL Institute of Information Security and Dependability.

Science Daily reports that the researchers have demonstrated a technique that uses ordinary Wi-Fi signals to identify people and map their surroundings without cameras or any device being carried by the person being observed. By watching how radio waves bounce around an environment, they essentially function like echolocation, revealing the shapes and movements of people as the signals bounce around a space.

You don’t even need to be connected to the network to get spied on. Other Wi-Fi devices nearby are transmitting a signal, providing enough information for the system to work. Turning off your phone won’t help you.

Your Wi-Fi Signal Could Be Used to See You Without a Camera

Beamforming feedback information is the data routinely exchanged by connected devices that helps Wi-Fi signals travel efficiently. Researchers analyzed this data and found that this method can work with standard Wi-Fi hardware, unlike previous systems that needed specialized equipment.

Add machine learning into the equation, and those radio wave measurements can be turned into images that identify people based on how they look and move. Once a machine learning model has been trained, identification can happen within seconds.

The team ran a test involving 197 participants in which the system reportedly identified people with almost 100 percent accuracy, regardless of viewing angle or walking style. This makes Wi-Fi-based surveillance potentially much more concerning than previously assumed, and probably more of a threat than a camera, because you can actually see a camera. If they are in your physical space.

Maybe it’s hiding in a teddy bear or whatever, but it’s there and findable. A Wi-Fi router just sits there, lights blinking on and off, while its invisible signals let anyone with tech know-how see you without actually seeing you. That’s why the researchers are calling for privacy protection to be built into future Wi-Fi devices.

Researchers warn that widespread wireless networks could eventually become an invisible surveillance infrastructure, particularly dangerous for protesters and other vulnerable groups. They are calling for privacy protections to be built into the forthcoming IEEE 802.11bf Wi-Fi standard.