Chrome May Let Users Mute Site Audio, Helping Prevent Audio Tracking

Google is working on a feature in its Chrome browser that would enable users to mute audio on websites on a site-by-site basis. The feature could help prevent an emerging kind of user tracking that employs ultrasonic signals.

The feature has shown up in the Canary build of Chrome, which is the early build that developers and other adventurous types run to get a preview of new features. In recent builds of Canary Google added a way for users to mute sound on each site through the address bar icon. Users need to go into the properties and enable the feature in the current build, but that may change if it makes it into the final public version of Chrome.

Some companies have begun providing technology to allow advertisers to track users’ movements around the web and across multiple devices. That technique relies on ultrasonic audio beacons embedded in advertisements that can be picked up by code in mobile apps. Websites can emit those signals, which are inaudible to humans, in the background while users are doing other things in their browsers.

The Federal Trade Commission has taken notice of this technique, and warned a dozen app developers about the inclusion of audio beacon technology in their apps. Security researchers also have been working on defenses against this technique. A group of academic researchers at University College London last year published a paper that outlines a defensive tactic against audio tracking that involves messing with the profile of a user that advertisers maintain.

“The idea is based on the fact that most advertising companies are maintaining interest (and usually behavioral) profiles for users. These profiles are built based on a variety of factors often including the ads that the user has previously seen. Given that the attacker can push beacons to the victim’s device, it can consequently influence the profile corresponding to the user. The degree that the attacker can “corrupt” this profile and what he can do with it, depends on how each company has implemented this mechanism,” Vasilios Mavroudis, one of the UCL researchers, said of the technique.

Features in Canary builds can take several months to show up in final versions of Chrome, depending upon developers’ priorities and other factors.