In the past few years, you’ve likely noticed that the sites, apps, and social media platforms you rely on are targeting you with advertisements and offers based on specific and demographic info about you that’s collected when you use any connected device. Recently, though, companies like Silicon Valley-based SilverPush have been taking consumer surveillance to a whole new level—one that, much to the concern of privacy-focused groups, capitalizes on microphone and speaker access on your various devices and gets them to do some very serious (and inaudible) whispering behind your back.

As The Atlantic explains, websites equipped with SilverPush tracking technology will cause the device you’re using to “emit an inaudible ultrasonic sound” that “any other devices you’ve got lying around” will be "listening" for if they’ve already been touched by SilverPush tech, too. Once the two SilverPush–enabled devices have done their ultrasonic call and response routine, the software has accomplished a very desirable feat in the world of consumer behavior-tracking: It’s established that your two or three (or more) devices are in close proximity to each other, and likely all have the same owner.

The company’s advantageous use of access to your devices’ microphones, speakers, and other hardware doesn’t end there, though; some TV ads now emit SilverPush’s ultrasonic audio beacon, too, which will be picked up by any "listening" devices nearby, allowing the company to get a very clear picture henceforth of how you interact with ads you see, and for how long.

Don't love the idea that your TV and smartphone might team up to share your personal info? The Center for Democracy & Technology (CDT) is right there with you; in a recent communique to the Federal Trade Commission [PDF], the nonprofit stressed that not only are users “often unaware of the wealth and detail of information that is being collected about their online and offline activities” by various cross-device tracking methods “and the significant privacy invasions that result,” but also that “tracking users through the use of audio beacons” and linking consumers’ devices with this method are “completely unexpected and outside of the control of the user.”

Joseph Lorenzo Hall, chief technologist for the CDT, is worried that such technology won’t just be used for working out how best to carpet-bomb consumers with ads, either. As The Atlantic explains, Hall worries that it could be used by governments for surveillance and could lead, for example, to “a group of dissidents in a country like China” being caught “meeting surreptitiously” should any “government-planted ultrasonic audio signal from a nearby TV” be picked up by the group’s devices and reveal that the owners were all together. 

SilverPush reportedly only operates in New Delhi at present (though the company maintains offices in the U.S.), so this particular kind of ‘listening in’ by our phones might not be commonplace in the States just yet. When it comes to the newest kinds of cross-device tracking, though, the CDT urges that the “best solution is increased transparency and a robust and meaningful opt-out system” for consumers—a policy goal that privacy advocates may need to do some serious cross-organizational collaboration to achieve.

[h/t The Atlantic]