Your Phone May Be Listening to Ultrasonic Signals for Better Ad Tracking: Report

For years, we’ve had phones with always-on listening capabilities. Starting with the first Moto X in 2013, followed by such devices as the Nexus 6 in 2014 and the iPhone 6s in 2015, many smartphones today can wake up from standby by saying hotwords like “Ok, Google” or “Hey Siri” respectively. Today the same technology is applied to smart home appliances like Google Home or the Amazon Echo.

Now, security experts based out of the University of California suggest that marketers could be tracking your behaviour by listening to ultrasonic signals using your phone’s microphone. WIRED reports that at the Black Hat Europe security conference, the group presented a set of tools to block this subtle tracking method.

The report suggests that marketers have been experimenting with ultrasonic audio signals - sound that is beyond the scope of what humans can hear - but something that a microphone of a smartphone can pick up. These audio signals can be embedded in traditional advertisements, webpages, or even physical locations like a retail store. Working in tandem with an app in your phone - that you’ve granted access to use the microphone - these signals can then be used to interpret which ads you watched, what sites you’ve visited, or even the places you’ve been.

Vasilios Mavroudis, a privacy and security researcher at University College London is worried that the only way to decipher these ultrasonic sounds is by capturing everything the microphone is receiving, including conversations you’re having around your phone.

Ultrasonic tracking technology has been in the works for some time, but it certainly hasn’t been favoured by everybody, due to privacy concerns. The Federal Trade Commission evaluated the tech in 2015, warning developers to avoid the use of this technology developed by a company called Silverpush.

Mavroudis suggests that the way forward is to have standards that won’t allow apps to listen in on all the ambient voices and sounds occurring next to a smartphone, just the ultrasonic kind useful for tracking. Until then, he and his team’s solution is to install software compatible with Android and Chrome, that will let users block anything the microphone picks up in the ultrasonic spectrum. This software will be available for download later this month.