Ordinary Wi‑Fi identifies people with 99.5% accuracy
Researchers at Karlsruhe Institute of Technology used standard Wi‑Fi routers to identify 197 people with about 99.5% accuracy by analyzing radio‑wave reflections, even when phones were off.
Researchers at the Karlsruhe Institute of Technology’s KASTEL Institute in Germany reported on May 22, 2026 that they built a system called BFId that uses ordinary Wi‑Fi routers to identify people by analyzing how radio waves reflect in a room.
BFId extracts signals from beamforming feedback data produced by consumer routers. The system collects reflection patterns across multiple antennas and time samples and processes those patterns to produce a signature tied to an individual’s body and movement. The method does not require a person to carry a phone or other electronic device.
In tests with 197 volunteers, the team reported an identification accuracy of about 99.5 percent. The experiments also showed the system could detect whether people were present, estimate their location inside a room and infer simple activities.
The hardware used in the study was off‑the‑shelf consumer routers rather than specialized laboratory equipment. The researchers described operational conditions that affect performance, including the placement and number of antennas and the need to collect enough feedback samples to build reliable signatures.
The research paper lists possible mitigations, such as filtering or randomizing beamforming feedback data, and notes those measures can reduce network performance or affect compatibility with existing devices.
The authors wrote, “We have shown robust identity inference with common off‑the‑shelf hardware which is already in widespread adoption in many homes and public areas.” The paper notes that ordinary networking gear that is widely deployed could be used for passive sensing.
The study documents technical results and potential defenses. It also notes that manufacturers of routers, operators of networks in homes and workplaces, and lawmakers may need to consider how to handle passive sensing capabilities and whether disclosure or limits are appropriate. Regulators and technology companies are focused on surveillance risks posed by connected devices.
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