Researchers from the University of Washington have developed a method to covertly track the activity of people in a room, and in some conditions, even beyond thin walls. The researchers demonstrated that a smartphone connected to a speaker or a television can be converted into an active sonar device, for tracking movements of people in the surroundings. The technology can potentially be used for covert surveillance purposes. The system is called CovertBand.
The audio equipment would send out periodic sonic pulses in the 18 to 20 kHz range. Sound waves in this frequency can be heard by adolescents, young children and pets, but adults have more difficulty in perceiving the low frequency sounds. To improve the accuracy of the method, the researchers increased the volume of the pulses, which brought them within the audible range. The researchers worked around this by masking the sound by playing regular songs on the equipment, along with the audio pulses.
Shyam Gollakota, senior author of the study said, "To our knowledge, this is the first time anyone has demonstrated that it is possible to convert smart commodity devices — like smartphones and smart TVs — into active sonar systems using music. And the physical information CovertBand can gather — even through walls — is sufficiently detailed for an attacker to know what the user is doing, as well as other people nearby."
The method can potentially work on any consumer electronics device with a speaker and a microphone, including smarthome hubs, smart TVs and smartphones. Software can automatically detect repetitive movements captured through CovertBand, but human analysis can be used for extracting more detailed information. The snoopers can be in close proximity to the targets, or on the other side of the planet. The technology is similar to Sonar Vision was used for covert surveillance of an entire city in the movie The Dark Knight Rises.