Ordinary WiFi Networks Can Now Identify People With Startling Accuracy
German researchers demonstrate new form of surveillance using radio waves, raising privacy concerns about ubiquitous wireless networks.
Researchers in Germany are warning that ordinary WiFi networks could become a powerful new form of invisible surveillance. Using standard wireless signals and artificial intelligence, they demonstrated a system capable of identifying people with striking accuracy, even if those individuals are not carrying an active device. "By observing the propagation of radio waves, we can create an image of the surroundings and of persons who are present," says Professor Thorsten Strufe from KASTEL—KIT's Institute of Information Security and Dependability. The system works similarly to a normal camera, but uses radio waves instead of light waves for recognition.
Turning off your smartphone is not enough to avoid detection, according to the researchers. Nearby wireless devices connected to the network still generate enough signal activity for the system to work effectively. "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," explains Strufe. "Thus, it does not matter whether you carry a WiFi device on you or not." The technology could transform everyday routers into quiet monitoring systems that operate without attracting attention, raising significant privacy concerns.
"This technology turns every router into a potential means for surveillance," warns Julian Todt from KASTEL. "If you regularly pass by a café that operates a WiFi network, you could be identified there without noticing it and be recognized later -- for example by public authorities or companies." Researcher Felix Morsbach notes that while intelligence agencies or cybercriminals currently have easier ways to monitor people, including hacked security cameras or internet-connected doorbells, WiFi networks pose a unique concern because they are nearly everywhere and largely invisible.
Unlike earlier experimental systems that relied on expensive sensors or specialized equipment, the new method works with ordinary WiFi hardware already found in most homes and businesses. Previous approaches often depended on channel state information, which measures how radio signals change after bouncing off walls, furniture, and people. The new technique instead takes advantage of normal communication between WiFi routers and connected devices, using beamforming feedback information that is transmitted without encryption and can potentially be read by anyone within range.
Wireless networks are now common in homes, offices, restaurants, airports, and public spaces across the world, giving this technology potentially enormous reach. The researchers emphasize that the omnipresent nature of wireless networks might create "a nearly comprehensive surveillance infrastructure with one concerning property: they are invisible and raise no suspicion." The discovery highlights growing concerns about privacy in an increasingly connected world where everyday technologies can be repurposed for surveillance without users' knowledge or consent.
