Popular smart TV models from Samsung and LG take screenshots several times a second and send them to manufacturers, even when the TV is used as an external display for a laptop or game console. This is stated in the NewScientist article.

Smart TV makers use those screenshots, as well as audio recordings, in their automatic content recognition systems that track people's TV viewing habits to deliver targeted ads. The researchers found that Samsung TVs can take screenshots once every 500 milliseconds, while LG TVs take screenshots once every 10 milliseconds.

"When a user connects his laptop to a TV via HDMI, just using the TV as a screen to watch something on the big screen with his laptop, he has no idea that his actions will be recorded," said Yash Vekaria, a lecturer at the University of California, Berkeley.

The researchers noted that the TVs don't take screenshots when watching streaming services from Netflix or other third-party apps, but when the TV is displaying content from a device connected to it via HDMI. The main concern is that screenshots may contain confidential information.

According to NewScientist, this behavior of TVs can be turned off by making appropriate changes in the settings.