Scientists in Germany have demonstrated a startling new form of surveillance: identifying people using nothing more than ordinary WiFi signals. By analyzing how radio waves bounce around a room, researchers can effectively “see” and recognize individuals — even if they are not carrying a device and even if their phone is turned off.
Very interesting concept. I was curious about how in the hell this could be done. This article explains the general method.
When an inert object like a person moves around between the router and stationary connected devices like computers and printers, it interferes with the signal. The pattern of interference plus math can be used to plot the movement of the object - and even measure subtle changes like hand gestures. Home security software from companies like Xfinity can already use this tech to send you an alert when something is moving around in your house, without needing additional hardware. Imagine an informercial where a guy holds up a handful of “clumsy motion sensors” with wires sticking out of them, and “confusing instructions”. Not if you just let your router do it!
As far as being a new and sinister means of surveillance, evil companies could already theoretically tap into anybody’s motion sensors or security cams. The difference with WiFi tracking is that you wouldn’t necessarily know it’s there.
That’s using CSI though. The article said the researches specifically did not utilize CSI.
But regarding CSI: I evaluated that as a small part of my Master’s thesis and it worked pretty OK for motion detection but not for classifying other activities, at least not on a SISO link. For more complex stuff you would need both a MIMO access point (router) and device (e.g. phone). Also, you need to constantly transmit messages to get up-to-date CSI, which is not great for power consumption as well as cluttering the communication channel. There are some other constraints, especially regarding noise. E.g. I managed to completely destroy the CSI spectrogram by turning on a microwave oven. There is 802.11bf in development, which is supposed to standardize this, because currently using CSI is pretty much a “hack”, as it is not intended for sensing. Once this is widely adopted, I would start being worried, but not right now.
This is from my thesis:
That is extremely cool, thank you.
Say waaaa?
inert meaning not a wifi device.