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Wi-Fi routers can now track you even without a smartphone
26 May 2026

Researchers from the Karlsruhe Institute of Technology (KIT) in Germany have developed a new tracking method that uses ordinary Wi-Fi routers to identify individuals.

The technique works by analyzing how human bodies interact with surrounding radio waves, and is accurate enough to recognize specific people even when they are not carrying any electronic devices.

This has raised major concerns over digital privacy and surveillance.

BFId attack method
Surveillance concerns

The KIT researchers have developed an attack method called BFId, which exploits a Wi-Fi feature called Beamforming Feedback Information (BFI).

This was introduced with Wi-Fi 5 technology to help routers optimize wireless performance by collecting feedback signals from connected devices.

However, these signals are continuously transmitted without encryption, allowing nearby WiFi devices to passively capture the information without users even knowing it.

Radio images
Identification process

Using machine learning models, the researchers analyzed these radio signals to create what they call "radio images" of people moving through a space.

This system works like a conventional camera but studies how human bodies alter the movement of radio waves instead of light.

In tests with 197 participants, the system identified individuals with an accuracy rate of 99.5%, regardless of their walking style or viewing angle.

Combining data to identify people
Data integration

While the system can't directly reveal someone's name or personal identity, attackers could combine Wi-Fi-generated tracking data with previously collected smartphone records or device information to identify individuals.

This makes the technology particularly concerning as people could be recognized repeatedly in public spaces without ever noticing the monitoring taking place.

Even turning off your phone may not protect you from this potential invasion of privacy.

Need for privacy protections
Response

The researchers have called on regulators and industry groups to introduce privacy protections into future Wi-Fi standards, especially the developing IEEE 802.11bf specification.

They warn that without safeguards, this technology could create a "nearly comprehensive surveillance infrastructure" that operates silently across public and private spaces.

The team also highlighted risks for political dissidents, activists, as well as protesters who intentionally avoid carrying smartphones to escape digital tracking.