The Federal Trade Commission (FTC) has issued a warning letter to a dozen app developers regarding the use of Silverpush framework for invasion of privacy.

Silverfish and alike designed some of their apps to use voice transmission from the handset’s microphone without the awareness of the users. The unnamed apps are using the intrusive tech to snoop the TV shows that users are watching. The said intrusive tech is able to produce a detailed log of the TV content being viewed while the user’s handset is turned on. It is for the sole purpose of targeted advertising software and analytics, Engadget reported. 

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It is not yet clear to what extent that this intrusive tech is taking place in the United States. FTC said on its letter that Silverpush has already used the inaudible sound to allow the brands keep tabs on user’s online presence across TVs and smartphones for over a year. The app makers have embedding the SilverPush code and asking for permission to use consumers’ microphones even though it is not required at all, according to Fortune. 

“The letters warn the app developers that if their statements or user interface state or imply that the apps in question are not collecting and transmitting television viewing data when in fact they do, that the app developers could be in violation of Section 5 of the FTC Act. The FTC provided guidance in a 2013 staff report on best practices for privacy disclosures in mobile apps,” FTC stated on its blog post. 

Silverpush is a cross-device mapping platform company that brings together data points from various digital services around the globe and associate it with people. One of its products is using a device’s microphone to check the ultrasonic sounds that would be able to distinguish if a user is using more than one device like smartphone and tablet all at the same time. Upon discerning this, it would allow the company to make an in-depth advertising profile based on the usage of device by the users.

The FTC did not identify the app developers but the letter indicated that they were from the Google Play store, giving away the hint that they are creating apps for Android-powered gadgets. However, it is not clear if they are into iOS devices as well.