Researchers demonstrate use of audio pulses to hack smartphones and fitness trackers

Researchers at the University of Michigan have demonstrated that acoustic pulses can be used to compromise the ubiquitous sensors used in electronic devices. The audio waves were designed to directly interfere with the commonly used accelerometer sensors in devices, that measure the movement of a device in three dimensions. The acoustic tones were successfully used to fool fifteen different sensors into registering movement that never occurred.

The research calls into question the basic tenet in consumer electronics that software can trust any input that comes from hardware. Kevin Fu, the associate professor of computer science and engineering who lead the research team said, “The fundamental physics of the hardware allowed us to trick sensors into delivering a false reality to the microprocessor. Our findings upend widely held assumptions about the security of the underlying hardware.” The team was able to use the acoustic tones as a backdoor, to make devices perform all sorts of actions.

A cheap speaker was used to make a Fitbit fitness tracker register five thousand phantom steps. A malicious audio file played back from a smartphone’s own speaker was used to control a linked remote control toy car. Another malicious audio file was used to make the accelerometer in a Galaxy S5 spell out the word “walnut” in a graph of its readings. The audio signals interfere with tiny springs in the accelerometer, the trick is similar to the phenomenon of an opera singer shattering a wine glass.