?Devices with Wi-Fi and Bluetooth support. Part2

Now back to the Wi-Fi access points. It has been reliably established that it is possible to track not only your location with high accuracy, but also body movements (position in space) directly through walls — by radio signals passing through a room or building.
And this is not the voice of a conspiracy theorist from under a foil cap - we offer you to get acquainted with the results of scientific research:

? "Recognition of a person's posture through a wall using radio signals", 2018 (published by the Massachusetts Institute of Technology, USA);
? "On the question of recognizing a person's pose in three-dimensional space using Wi-Fi technologies", 2020 (published by the University of New York Press in Buffalo, USA);

You can see the technology itself in action (2018), for example, here and here (2020).

Similarly, with the help of Wi-Fi alone, it is possible to count the number of people in a certain space (yes, including directly through walls) — both in motion ("Counting the number of people in a group through walls using WiFi technologies", 2018) and conditionally stationary. In fact, a person usually cannot maintain complete immobility for a long time, and periodically "fidgets"; at such moments, his movements are recorded using Wi-Fi. See a brief presentation of the results of the 2021 study and a video demonstrating the technology.

The function of randomizing MAC addresses, by the way, is also not a panacea. Modern device identification systems based on trial requests demonstrate an accuracy of about 95%, allowing, for example, to estimate the number of people present at an event, almost in real time:

"BEFOROS: a low-cost Wi-Fi-based monitoring system for assessing the occupancy of public places" (2020).

In general, such developments suggest a whole ensemble of application options. For example, you can record all visitors to certain buildings/premises (say, hotels, hospitals or embassies), then find out who meets whom inside, and then track the person of interest already outside the perimeter. Even if one or another visitor does not have a smartphone with him.

Strictly speaking, there are only two ways to counteract this:

?Completely shield the entire building (or a separate room) according to the type of Faraday cage; 
?Eliminate any possibility of linking a digital cast to you personally.