Researchers from Sweden and the UK found an innovative way to steal smartphone unlock patterns. They can achieve that by transforming a smartphone into an echo-locator. The technique is called SonarSnoop and turns a smartphone’s speaker and microphone into a sonar.

How is that possible? A malicious Android hack app installed on a smartphone could instruct the device to generate sound waves. These would come out of the phone’s speaker, but resonate at frequencies that human ears could not discern, between 18kHz and 20kHz. These sound waves are used to track a finger’s motion and/or position on the screen.

The smartphone’s microphone is then used to pick up these sound waves, which, just as with sonars, bounce off objects. In this particular example, the user’s finger. Since not all smartphones have their microphones and speakers in the same place, machine learning could be employed. It could learn to collect and decode the signals, and then predict the unlock pattern used.

As for the success rate of SonarSnoop, a research from Lancaster University in the UK and Linköping University in Sweden, claims it is in early stages. It managed, however, to reduce the number of unlock pattern possibilities by 70%. The researchers detail the methodology in the paper (source link), using a Galaxy S4.

Tell us: is this the coolest Android hack, or what?