The Federal Trade Commission announced yesterday it has issued warning letters to app developers who have installed software that can monitor a device’s microphone to listen for audio signals that are embedded in TV ads.

Known as Silverpush, the software is reportedly designed to monitor consumers’ TV use through audio beacons emitted by TVs, which consumers can’t hear but can be detected by the software. The letters note that the software would be capable of producing a detailed log of TV content viewed while a user’s mobile device was turned on for the purpose of targeted advertising and analytics.

The letters note that Silverpush has stated publicly that its service is not currently in use in the United States, but it encourages app developers to notify consumers that their app could allow third parties to monitor consumers’ TV viewing habits should the software begin to be used in this country.

“These apps were capable of listening in the background and collecting information about consumers without notifying them,” Jessica Rich, director of the FTC’s Bureau of Consumer Protection, says. “Companies should tell people what information is collected, how it is collected, and who it’s shared with.”

The warning letters state that app developers ask users for permission to use the device’s microphone, despite the apps not appearing to have a need for that functionality. The letters also point out that nowhere do the apps in question provide notice that the app could monitor TV viewing habits, even if the app is not in use.

Lesley Fair, an attorney with the FTC’s Bureau of Consumer Protection, puts it simply in her March 17 blog: It’s not a good idea to collect information that consumers wouldn’t expect.

“After suggesting that developers read Marketing Your Mobile App: Get It Right From the Start, the letters end with the verbal equivalent of that point-to-our-eyes and then point-to-you universal symbol for ‘We’re monitoring this,’ ” Fair says.