From signals to surveillance: How WiFi tracks human activity through walls

Imagine a world where your WiFi router does not just provide internet, but it also acts as a set of “digital eyes” that can see your body’s posture and movement through walls.

That is the core of DensePose from WiFi, a breakthrough in "device-free" sensing. It was originally developed by researchers at Carnegie Mellon University (CMU), but this technology has drawn public attention due to new open-source systems.

A new open-source edge AI system called RuView is turning the normal WiFi router into an everyday tracker detecting body pose, vital signs, and movement patterns without a single camera.

RuView is a high-speed signal processing system that exploits WiFi Channel State Information (CSI) to reconstruct 3D human poses and extract vital signs. It also analyses how the WiFi waves scatter when they bounce off human bodies. 

The technology uses 4-6 tiny and inexpensive WiFi chips placed around a room. Together they create an invisible web of radio waves.

A fast AI program analyzes these tiny disruptions 54,000 times per second. It’s so sensitive that it can map out 17 points on your body, essentially creating a digital stick figure of your head, elbows, and knees in real-time.

Privacy concerns

The technology poses a threat to users’ security and privacy. Unlike cameras, passive WiFi sensing is invisible and highly unregulated by current General Data Protection Regulation (GDPR). One can easily exploit WiFi networks to keep an eye on someone’s activity and presence.

The lack of consent in passive sensing also compounds privacy risks. According to legal analysis, in the case of passive sensing, it is quite difficult to obtain a consent, thereby leading to the total collapse of consent frameworks.

Moreover, unlike cameras, even the darkness or physical barriers cannot protect the user from being spied on. As this tacking occurs at the physical layer, network encryption protocols like WPA3 cannot stop it.

It is no mistake to say that when devices designed for communication suddenly become sensors and trackers, it changes the privacy landscape.