Your WiFi router could soon identify you even without a smartphone, researchers warn

You may no longer need a smartphone, smartwatch or connected gadget to be digitally tracked. According to researchers in Germany, simply walking through a room with WiFi signals could soon be enough.

Scientists from the Karlsruhe Institute of Technology (KIT) have revealed a new tracking method that uses ordinary WiFi routers to identify individuals by analysing how their bodies interact with surrounding radio waves. The researchers say the technique is accurate enough to recognise specific people even when they are not carrying any electronic devices.

The study has sparked fresh concerns over privacy and surveillance, particularly because the technology relies on infrastructure already embedded almost everywhere — homes, cafés, airports, offices and public buildings.

Unlike CCTV cameras or facial-recognition systems, the tracking remains effectively invisible.

How WiFi signals can ‘see’ people

The researchers developed an attack method called BFId, which exploits a WiFi feature known as Beamforming Feedback Information (BFI). Introduced with WiFi 5 technology, BFI helps routers optimise wireless performance by collecting feedback signals from connected devices.

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The problem, according to the researchers, is that these signals are continuously transmitted without encryption.

That means nearby WiFi devices can passively capture the information without users realising it.

Using machine learning models, the researchers analysed these radio signals to generate what they describe as “radio images” of people moving through a space. Instead of using light, like a conventional camera, the system studies how human bodies alter the movement of radio waves.

“By observing the propagation of radio waves, we can create an image of the surroundings and of persons who are present,” researcher Thorsten Strufe explained. “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.”

In tests involving 197 participants, the system reportedly identified individuals with 99.5 per cent accuracy, regardless of their walking style or viewing angle.

Researchers believe this makes the technology particularly concerning because people could potentially be recognised repeatedly in public spaces without ever noticing the monitoring taking place.

Why experts fear mass surveillance

The researchers stressed that the system alone cannot immediately reveal someone’s name or personal identity. However, if attackers combine the WiFi-generated tracking data with previously collected smartphone records or device information, identifying individuals becomes far easier.

Perhaps more worrying, turning off your phone may not protect you.

As long as WiFi devices nearby continue communicating with a network, the radio waves remain active and continue mapping the environment and anyone moving through it.

“This technology turns every router into a potential means for surveillance,” warned study author Julian Todt.

“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.”

The researchers argue the real danger lies in how seamlessly such systems could blend into daily life. While cameras are visible and often regulated, WiFi routers are considered harmless background infrastructure.

The paper warns this could eventually create a “nearly comprehensive surveillance infrastructure” operating silently across public and private spaces.

Researchers also highlighted the risks for political dissidents, activists and protesters who intentionally avoid carrying smartphones to escape digital tracking. According to the team, radio-based identification systems could undermine those precautions entirely.

The scientists are now urging regulators and industry groups to introduce privacy protections into future WiFi standards, particularly the developing IEEE 802.11bf specification.

Without safeguards, they warn, the same technology powering faster wireless connectivity could also reshape the future of surveillance in ways most people would never see coming.