What your smart TV knows about you - and how to stop it harvesting data

Watching TV feels like a benign pastime, but as all TVs become "smart" - connected to the internet via your router - they are gaining the ability to watch you too. As soon as you switch them on, smart TVs made by the likes of LG, Samsung and Sony are gathering data from the TV itself, as well as from the operating system and apps. Then there are the devices you plug into your TV, such as Google's Chromecast, Apple TV and Amazon's Fire Stick.

A TV is no longer just a device for showing you content - it has become a two-way mirror allowing you to be observed in real time by a network of advertisers and data brokers, says Rowenna Fielding, director of data protection consultancy Miss IG Geek. "The purpose of this is to gather as much information as possible about your behaviour, interests, preferences and demographics so it can be monetised, mainly through targeted advertising."

Smart TV spying is difficult to avoid. A study by researchers at Northeastern University and Imperial College London found data from TVs and smart devices was sent to Google's ad business and to Netflix, even if people didn't have Netflix.

The data collected by your smart TV depends on its manufacturer, brand and version. In theory, most smart TVs are capable of collecting audio, video and TV usage data, says Toby Lewis, global head of threat analysis at cybersecurity company Darktrace.

Voice activation is one feature with the potential to gather large amounts of data. Microphones and software are listening for instructions and they can capture conversations and other sounds within range. These recordings might be sent to third parties to be analysed.

Cross-device tracking is another issue to consider. Data collected via your smart TV is more valuable when combined with information from other smart devices such as mobile phones, laptops and home automation gear, according to Fielding. "This allows individuals to be profiled in detail: geo-location history, web browsing activity and social media information can be added to TV data."

Then there are the cookies and trackers. Apps and browsers on smart TVs use cookie- and pixel-tracking technologies just like websites do to track, recognise and identify devices for user-profiling. "Most apps installed on your smart TV will be snitching to a large network of advertisers and data brokers," Fielding warns.