Imagine being at home making a coffee and someone not far from your router can reconstruct your posture, your steps, even your identity using invisible waves. This is exactly the type of scenario that researchers at Kit, the German Institute of Technology, are demonstrating is already possible.

The team at the KASTEL, Institute for Information Security and Reliability, led by men like Thorsten and with contributions from Julien Todt, demonstrated that the method developed by them is capable of identifying individuals using only Wi-Fi signals, without the need for cameras, special sensors or connected personal devices.

The technique analyzes how radio signals propagate and reflect in an environment, creating a kind of invisible image that reveals presence, posture and movement with a precision comparable to a photograph. According to Professor Thorsten Struff, the process works similarly to a regular camera, but instead of light it converts radio waves into a visual representation.

And the most disturbing detail, it does not matter if the person carries a device or not, even if the devices are turned off, other nearby active routers or devices are enough to generate the necessary data. The team explains that by observing the feedback signals routinely transmitted by Wi-Fi networks, the so-called AS BFI training information, it is possible to reconstruct the silhouette and movement of a person.

These signals are not encrypted and can be collected by third parties, making the method accessible and difficult to detect. In tests with 197 participants, scientists were able to recognize individuals with almost 100% accuracy, even with different walking styles or from different angles. Researcher Julien Todt believes that any common router can become a surveillance tool.

A simple cafe with active Wi-Fi could theoretically record the presence of someone passing by repeatedly without the person ever knowing, with wireless networks present in almost every place, from houses to squares, the risk of this technology evolving into an invisible tracking system is real.

Although the study has scientific purposes, the group itself recognizes the worrying potential of the finding: Wi-Fi, an essential tool for daily life, could become a ubiquitous surveillance infrastructure capable of mapping and identifying people in real time.