[notepad0x90]

Yes, but things could be refined. With more resources and research thrown at it, it could become more versatile, that's why the title of the post says "could". And chances are, there are private and government entities already doing this. Research like this has been coming out for at least a decade now.

Even Xfinity has motion detection in homes using this technique now:

https://www.xfinity.com/hub/smart-home/wifi-motion

[SubiculumCode]

This has already been an area of research, both publicly, and most likely in private/government defense research. In a targeted situation, i.e. surveillance of a household of 6, this would work easily enough...but I doubt there is enough information to provide reliable (high AUC) tagging of ID in a public scenario oh hundreds to thousands of individuals.

[transpute]

https://www.theregister.com/2025/07/22/whofi_wifi_identifier...

> Researchers in Italy have developed a way to create a biometric identifier for people based on the way the human body interferes with Wi-Fi signal propagation.. can re-identify a person in other locations most of the time when a Wi-Fi signal can be measured. Observers could therefore track a person as they pass through signals sent by different Wi-Fi networks – even if they’re not carrying a phone.. their technique makes accurate matches on the public NTU-Fi dataset up to 95.5 percent.

[Retric]

That’s 95.5% accuracy with a 16 person dataset in a highly constrained environment.

Wi-Fi uses long wavelengths, you can cancel out the noise with one person but crowds are all distorting the same very weak signal here. 5Ghz = 6cm, visible light is 380 to about 750 nanometers.

[Ancapistani]

I bet there is.

Off the top of my head, I bet body composition combined with gait analysis would be enough to uniquely identify an individual.

[eth0up]

Xfinity's is sensitive enough to configure for animals or humans under 40-70lbs, I forget the exact number.

From my minimal research, it could be pushed a lot further.

What I'm particularly interested in is the edge case scenario of duplexes and apartments, where neighbors are unwittingly subjected to surveillance. There is little more to their routers than firmware to impart these capabilities. No reason to think it won't become common, and there are a handful of other companies basically offering just this as a service.

Strange times.

Edit: I should have mentioned the obvious, that pesky thing no one wants to address... When AI is added to this tech, it will get grotesque. Gait recognition, behavioral patterning, etc. Not something to sneeze at.

Possibly what was used to watch Maduro, along with synthetic aperture radar etc.

[notepad0x90]

if it's a public scenario, you don't need that, they're using wifi on people's persons to id them. The concern is more gait analysis, and by some accounts even lip reading is possible with mm-wave 5g.

[thesuitonym]

Yeah, it can and will be refined, but the major limiting factor is resolution. Wi-Fi radio waves are just too big to get a very clear image.

[Noaidi]

6 cm is too big? It’s big enough to get an idea of people moving around. And what about the 5 cm wave of 6G Wi-Fi?

But then we can talk about all the millimeterwave signals that are bouncing around everywhere.

[BobbyTables2]

What about 5G cellular? It already supports millimeterwave bands!

[notepad0x90]

like i mentioned in another comment, do you really need good resolution for gait analysis? You also have people carrying their phones inside the house all the time, so you know what bssid is associated with that coarse movement. and if you have access to their ap/router combo, you can tell what IP that device has and what domains it's been visiting.

Let's say you visit a friend in a different city, the same ISP controlling their router, can use your mac, but even if you turn off your wifi or leave your phone in your car, your volume profile and gait can betray you. how you sit, how you lean, how you turn. I'd wager, if 6-10 distinct "points" can be made out and associated with a person, that's all that's needed to uniquely identify that person after enough analysis of their motion, regardless of where they go in the world.

Imagine if they're not using one AP, but using your neighbors AP as well, two neighbor APs and your own can triangulate and refine much better.

[mvanbaak]

for now ...

[XorNot]

No this is fixed by physics. 5ghz waves are about 60mm wavelength.

Your resolution limit is about 30mm as a result.

[anu7df]

Add a nice prior from a photograph, combine multiple measurements and presto you can pick out a person from a crowd with reasonable accuracy. No?

[accidentallfact]

It applies to the sensor size as well. Such as you need a 3m sensor to get 100px per radian, under ideal circumstances, unless I'm mistaken. (I think I'm not)

[NetMageSCW]

There are techniques that can reduce that limit when you have multiple signals, though whether they can be combined with this technique isn’t clear.

[jazzyjackson]

Wifi 7 includes 6Ghz band but fair enough

[Aurornis]

> Even Xfinity has motion detection in homes using this technique now

WiFi presence detection is a completely different problem. If the WiFi environment is changing past a threshold, return a boolean yes or no. It can't actually tell if someone is present or if the environment is just changing, such as a car driving close enough to reflect signals back in a certain way.

Doing mass surveillance where you detect individual people in a random home environment isn't the same thing at all. All of these "could" claims are trying to drawn connections between very different problems.

[notepad0x90]

You'll have to explain that a bit more. Isn't the threshold detection analyzing radio signal data? For identifying people, you don't need to reconstruct their face or fingerpring using that data. you just need to fingerprint them.

With gait analysis for example, it's only looking at a handful of data points, the way we walk is very unique. lip-reading, i can see how that's a stretch, but out movement patterns and gait are disturbances in radio waves. If you're using just one person's wifi, that sounds difficult, but if you're collecting signal from multiple adjacent wifi access points, it's more realistic to build a very coarse motion representation, perhaps with a resolution no finer than 1 cubic ft, but even with more coarse representations, gait can be observed.

Even gait aside, the volume profile of a person and their location in the house alone are important data points, couple that with the unique wifi identifier or IP, you can make a really good guess at who the person is, and what room they're in.

[appletrotter]

Insufficient granularity of data

[sandworm101]

Only if wifi is radically increased in frequency, power, directionality or antenna size. And i mean way beyond practicallity. It would be easier to identify people by the sounds of thier footsteps, something easily done through anything with a microphone. With three microphones, you can track that movement to the inch.

[notepad0x90]

or if wifi from mobile devices, and your neighbor's APs and their wifi devices is collated to build a fine-enough picture of movements.