Using Wi-Fi to see through walls
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The surveillance technique is called variance-based radio tomographic imaging and works by visualizing variations in radio waves as they travel to nodes in a wireless network. A person moving inside a building will cause the waves to vary in that location, the researchers found, allowing an observer to map their position.
The researchers, electrical engineering graduate student Joey Wilson and his faculty advisor Neil Patwari, have tested the technique with a 34-node wireless network using the IEEE 802.15.4 wireless protocol, according to the MIT Technology Review. By “interrogating” the space with signals and multiple receivers, the researchers found they were able to read the waves to detect the location of a moving object within a meter of accuracy.
Wi-Fi blocking paint
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Researchers say they have created a special kind of paint which can block out wireless signals. It means security-conscious wireless users could block their neighbours from being able to access their home network - without having to set up encryption.