Your Wi-Fi might be spying on you—even if you’re not connected. Researchers at the Karlsruhe Institute of Technology (KIT) have unveiled a chilling discovery: it’s possible to identify individuals solely through Wi-Fi signals, even when they aren’t carrying a smartphone or tablet. This revelation marks a significant leap in the surveillance capabilities of ordinary technology and raises urgent questions about digital privacy and civil rights.
Wi-Fi waves as invisible cameras
According to Professor Thorsten Strufe from KIT’s Institute of Information Security and Dependability (KASTEL), Wi-Fi networks can act much like cameras—except they use radio waves instead of light. By analyzing how radio waves propagate and reflect off objects and people, researchers can generate detailed images that reveal who is nearby. This process, Strufe explains, can identify individuals even if they have no device on them.
“Switching off your phone doesn’t help,” Strufe notes. “As long as other Wi-Fi devices in the area are active, the system can capture and identify you.”
Every Wi-Fi router becomes a potential spy
The study’s co-author, Julian Todt, warns that this technology effectively turns every Wi-Fi router into a potential surveillance device. Simply walking past a café, office, or home with an active Wi-Fi network could expose your identity. Over time, such data could be used for tracking movement patterns, profiling individuals, or even assisting government or corporate surveillance efforts.
While existing methods like CCTV cameras are already common, the ubiquity of Wi-Fi makes this approach far more pervasive. “Wireless networks are everywhere,” Strufe adds. “If exploited, they could create an invisible surveillance web spanning homes, offices, and public spaces.”
No special hardware needed—just your router
Unlike older techniques that required specialized sensors or access to complex radio data, this new method works with standard Wi-Fi devices. It uses something called beamforming feedback information (BFI)—signals that Wi-Fi devices send back to routers to optimize connectivity. These feedback packets are unencrypted, meaning anyone intercepting them can analyze the reflections and build images of people nearby.
Once trained on a machine learning model, this system can identify individuals within seconds—and with startling precision. In tests involving 197 participants, the researchers achieved an identification accuracy close to 100%, regardless of walking style or camera angle.
A privacy nightmare in the making
While the research demonstrates impressive technical potential, it also highlights a dangerous new threat to privacy. In democratic societies, it could lead to new debates over data protection and surveillance oversight, while in authoritarian regimes, it could become a tool for tracking protesters or dissidents without consent.
Strufe and his colleagues are urging the inclusion of strong privacy safeguards in upcoming Wi-Fi standards, particularly IEEE 802.11bf, to prevent the misuse of this capability. As they prepare to present their findings at the ACM Conference on Computer and Communications Security (ACM CCS 2025) in Taipei, one thing is clear: the Wi-Fi networks we trust may soon become the eyes of an invisible surveillance system.
Conclusion
This discovery underscores the growing convergence between convenience and vulnerability in modern technology. Wi-Fi networks—once viewed as harmless digital utilities—are now proving to be powerful surveillance instruments. The challenge ahead is to balance innovation with privacy, ensuring that the invisible waves connecting us don’t become tools to control us.
