WiFi could become an invisible mass surveillance system

Can you say what products make use of this technique? i.e. is it well known like Juniper Mist or not publicly available?

It's at least possible to record heart rate with wifi, so that suggests a broad variety of biometrics can be recorded.

https://arxiv.org/abs/2510.24744

What happens is that a large body of water (pun intended) has the ability to absorb and reflect wifi signals as it moves through the room. For this you need to generate traffic and measure for instance RSSI or CSI (basically, signal strength) of the packets. If you increase frequency you can detect smaller movements such as arms moving vs. a body, or exclude pets if you reduce sensitivity. It works well for detecting presence and movement in a defined space, but ideally requires you to cross the path between two mains-powered devices, such as light bulbs or wifi mesh points. Passing a cafe doesn't seem too likely.

If you want to do advanced sensing, trying to identify a person, I would postulate you need to saturate a space with high frequency wifi traffic, ideally placed mesh points, and let the algo train on identifying people first by a certain signature (combination of size/weight, movement/gait, breath / chest movements).

Source: I worked on such technologies while at Signify (variants of this power Philips/Wiz "SpaceSense" feature).

More here: https://www.theverge.com/2022/9/16/23355255/signify-wiz-spac...

I don't feel that this article is a fair summary of the paper. And the title is just clickbait.

The paper says, in a somewhat contrived scenario, with dozens of labelled walkthroughs per person, they can identify that person from their gait based on CSI and other WiFi information.

This is a long way from identifying one person in thousands or tens of thousands, being able to transfer identifying patterns among stations (the inference model is not usable with any other setup), etc.

All the talk of "images" and "perspectives" is journalistic fluffery. 2.4Ghz and 5Ghz wavelengths (12cm & 6cm) are too long to make anything a layperson call an "image" of a person.

What creepy thing could you actually do with this? Well, your neighbor could probably record this information and tell how many and which people are in your home, assuming that there is enough walking to do a gait analysis. They might be able to say with some certainty if someone new comes home.

That same neighbor could hide a camera and photograph your door, or sniff your WiFi and see what devices are active or run an IMSI catcher and surveil the entire neighborhood or join a corporate surveillance outfit like Ring. Using the CSI on your WiFi and a trained ML model is mostly cryptonerd imaginiation.

Microwave frequencies like 2.4 or 5 GHz just passively allow you to do this. You'd have to adopt frequencies that are useless for radar.

I mean you could even jam a microwave oven door open, turn it on, and then measure how much energy loss there was through certain paths. That's essentially all beamforming in Wifi requires -- a really sophisticated way of measuring paths that cause energy loss, and a really sophisticated antenna design that allows you to direct the signal through paths that don't cause energy loss. The first problem is what's facilitating surveillance because humans cause signal loss because our bodies are mostly water, and 2.4 GHz radio waves happen to get absorbed really well by water. This causes measurable signal loss on those paths and the beamforming antennae use that information to route around your body. But they could also just log that information and know where you are relative to the WAP.