Electronic surveillance

Wi-Fi “Vision” Poses Security Threat

New research shows that ordinary Wi-Fi signals from smartphones can be used to “see” behind closed doors and track individuals in their own homes.

A group of scientists led by Yanzi Zhu at the University of California, Santa Barbara, have found a way to see through walls using ambient Wi-Fi signals and an ordinary smartphone.

They say the new technique allows an unprecedented invasion of privacy: “Bad actors using smartphones can localize and track individuals in their home or office from outside walls, by leveraging reflections of ambient Wi-Fi transmissions”, according to technologyreview.com.

This Wi-Fi based tracking technology looks for changes in an ordinary Wi-Fi signal that reveal the presence of humans. A Wi-Fi “vision” would make walls and doors almost transparent. Wi-Fi “light” is the signal coming out of transmitters, and people as well as other bodies can be tracked according to how they reflect this “light”.  

But this is not done by producing an image. The data that Zhu and colleagues use is just a measurement of the signal strength at a specific location. That doesn’t tell you anything about the location of the transmitter. And without knowing that, it’s impossible to say where any human that distorts the field would be.