More than 250 apps available on Google Play Store are able to monitor a user through their smartphone microphones, with data generated used for marketing purposes, The New York Times (NYT) revealed.

Once name-dropping gaming apps including Pool 3D and Beer Pong: Trickshot are downloaded they are able to monitor the TV viewing habits of users even when the games are not being played, NYT reported.

The apps in question use software from a start-up called Alphonso, which collects and sells TV-viewing data to advertisers to enable them to target ads effectively and gain further insight into consumers.

NYT, which interviewed Alphonso’s CEO Ashish Chordia, said the software uses a smartphone’s microphone and can identify what is being watched by identifying audio signals in TV ads, and even match the information with the places people visit or movies they see.

An example could be analysing what ads prompted someone to visit a car dealership. In other cases, the software can also reportedly detect certain sounds even if a phone is in a pocket, as long as the apps are running in the background.

Alphonso, however, clarified it does not record an app user’s conversations and it also needs permission from the user to gain access to their microphone and locations. Chordia added its software complies with the US Federal Trade Commission’s guidelines and consumers have the option to opt-out at any time.

The company did not reveal exactly how many people it was generating data from. In total, 1,000 games and social apps use the software, with a small number also available on Apple’s App Store.