A team of researchers at Karlsruhe Institute of Technology has demonstrated something unsettling: WiFi routers in your neighborhood can identify you without you carrying a phone, without you connecting to them, and without you knowing it's happening.
The method works by analyzing how radio waves bounce off people's bodies as they move through a space. Think of it like a camera that uses invisible radio signals instead of light. When devices connected to a WiFi network exchange data with the router, they send unencrypted feedback signals that reveal these patterns. A machine learning model trained on this data can identify individuals with nearly 100% accuracy, regardless of their angle or how they walk.
"By observing the propagation of radio waves, we can create an image of the surroundings and of persons who are present," explains Professor Thorsten Strufe, a cybersecurity expert at KIT. "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."
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Start Your News DetoxWhat makes this particularly concerning is the invisibility and ubiquity of the threat. You can't protect yourself by turning off your own device—the router picks up signals from other people's phones and laptops nearby. Walk past a café with WiFi, and you could be identified without noticing. Walk through an office building, a train station, a shopping mall, and the same applies. WiFi networks now exist in most homes, offices, and public spaces.
The gap between capability and safeguards
The researchers tested their method on 197 participants and achieved nearly perfect accuracy. They didn't need specialized hardware—just a standard WiFi device and access to the unencrypted beamforming feedback that routers exchange with connected devices.
Julian Todt, another researcher on the team, notes the darker implications: "This technology turns every router into a potential means for surveillance. 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."
Intelligence agencies and criminals already have simpler surveillance tools—CCTV cameras, video doorbells, phone tracking. But those are visible. They announce themselves. This doesn't. As Felix Morsbach observes, "The omnipresent wireless networks might become a nearly comprehensive surveillance infrastructure with one concerning property: they are invisible and raise no suspicion."
The risk is especially acute in authoritarian states, where such technology could be weaponized to monitor protesters or dissidents.
What happens next
The researchers are pushing for privacy protections to be built into the upcoming IEEE 802.11bf WiFi standard before this capability becomes widespread. It's a call for prevention rather than reaction—a chance to embed safeguards into the technology itself rather than trying to retrofit them later. Whether that happens depends on how seriously the WiFi industry and regulators take the warning.
