The growing concern over online data and user privacy has been focused on tech giants like Facebook and devices like smartphones. But people’s data is also increasingly being vacuumed right out of their living rooms via their televisions, sometimes without their knowledge.

In recent years, data companies have harnessed new technology to immediately identify what people are watching on internet-connected TVs, then using that information to send targeted advertisements to other devices in their homes. Marketers, forever hungry to get their products in front of the people most likely to buy them, have eagerly embraced such practices. But the companies watching what people watch have also faced scrutiny from regulators and privacy advocates over how transparent they are being with users.

Samba TV is one of the bigger companies that track viewer information to make personalized show recommendations. The company said it collected viewing data from 13.5 million smart TVs in the United States, and it has raised $40 million in venture funding from investors including Time Warner, the cable operator Liberty Global and the billionaire Mark Cuban.

Samba TV has struck deals with roughly a dozen TV brands — including Sony, Sharp, TCL and Philips — to place its software on certain sets. When people set up their TVs, a screen urges them to enable a service called Samba Interactive TV, saying it recommends shows and provides special offers “by cleverly recognizing onscreen content.” But the screen, which contains the enable button, does not detail how much information Samba TV collects to make those recommendations.