Smart TVs are tracking what you watch—even when you use them as external screens, according to a recent study by researchers from Universidad Carlos III de Madrid (UC3M), University College London, and the University of California, Davis.

The study reveals that these TVs send viewing data to their servers, allowing manufacturers to build detailed profiles of users and tailor advertisements based on their habits.

The researchers found that smart TVs use a technology called Automatic Content Recognition (ACR) to capture screenshots or audio of the content on the screen.

This data is then sent to servers regularly, even if the TV is being used as a monitor connected to a laptop or gaming console.

“ACR works like a visual version of Shazam,” explains Patricia Callejo, a professor at UC3M and a fellow at the UC3M-Santander Big Data Institute.

“It takes snapshots or audio of what’s on your screen to create a profile of your viewing habits. This allows TV manufacturers to track user behavior as accurately as websites track activity online.”

The study, presented at the Internet Measurement Conference (IMC 2024) in Madrid, showed that smart TVs from brands like Samsung and LG collect and transmit data frequently. Samsung TVs sent data to servers every minute, while LG devices transmitted information every 15 seconds.

This tracking happens regardless of how the TV is used—whether it’s for traditional television viewing or as a screen for connected devices like laptops or gaming systems. “The intensity of this monitoring is concerning,” Callejo said.

“These platforms are collecting huge amounts of data about users, often without their awareness.”

The researchers also tested whether privacy settings on smart TVs could block ACR tracking. While it is possible to prevent data collection by manually adjusting the settings, the study found that ACR is enabled by default. Many users are either unaware of this or don’t know how to change their settings.

“The lack of transparency in these default settings is a big problem,” Callejo added. “Most people don’t realize their TV is tracking their activity, let alone how to stop it.”

This research highlights the growing privacy concerns with smart devices connected to the Internet of Things (IoT).

It also calls for more action from manufacturers and regulators to ensure users have clear and simple ways to protect their privacy.

As smart TVs and other IoT devices become more common, the study underscores the urgent need for better privacy safeguards to prevent them from becoming unchecked surveillance tools.