• by Wendy Davis , Staff Writer @wendyndavis, March 17, 2016

Last October, the Center for Democracy & Technology called attention to SilverPush -- a tracking software that can monitor people's television use by embedding "audio beacons" in TV ads.

Those beacons are inaudible to people, but can be detected by the software, which comes bundled with mobile apps. The software activates microphones in the phones, which then pick up the beacons and can compile a log of TV programs viewed while the smartphone was turned on.

News of this technology understandably alarmed privacy advocates, who point out that people never imagine they will be subject to this kind of surveillance while watching TV in their living rooms.

"This tracking crosses all kinds of lines,” Alvaro M Bedoya, founding executive director of the Center on Privacy & Technology at Georgetown Law, told Forbes last year. “People simply do not expect that while they’re watching TV with their families, their phones will be silently listening for sounds inaudible to human ears -- that will then allow a company they’ve never heard of to track them more effectively."

SilverPush reportedly has said the technology is in use in India, but not in the U.S. But even if the tracking technology is not currently used in this country, it's available and has been incorporated into at least a dozen apps offered on Google Play, according to the Federal Trade Commission.

Today, the agency made clear to developers of those apps that they should not use this technology without people's knowledge.

"Upon downloading and installing your mobile application that embeds SilverPush, we received no disclosures about the included audio beacon functionality -- either contextually as part of the setup flow, in a dedicated standalone privacy policy, or anywhere else," Maneesha Mithal, associate director at the agency's privacy division, wrote in warning letters sent to 12 developers. "If your application enabled third parties to monitor television-viewing habits of U.S. consumers and your statements or user interface stated or implied otherwise, this could constitute a violation of the Federal Trade Commission Act."

Mithal points out in the warning letter that the software can access devices' microphones even when the app isn't in use. "Moreover," the letter continues, "your application requires permission to access the mobile device’s microphone prior to install, despite no evident functionality in the application that would require such access."

The FTC did not name the companies it warned today.