Watching TV with the Second-Party: A First Look at Automatic Content Recognition Tracking in Smart TVs

TL;DR

This study investigates how smart TVs use Automatic Content Recognition (ACR) to track viewing habits, revealing that ACR operates across different viewing modes, can be blocked by privacy controls, and varies between the UK and US.

Contribution

It provides a systematic black-box analysis of ACR network traffic, highlighting privacy implications and cross-region differences in smart TV tracking practices.

Findings

ACR functions even when TVs are used as external displays

Opting out can stop ACR network traffic

There are regional differences in ACR tracking behavior

Abstract

Smart TVs implement a unique tracking approach called Automatic Content Recognition (ACR) to profile viewing activity of their users. ACR is a Shazam-like technology that works by periodically capturing the content displayed on a TV's screen and matching it against a content library to detect what content is being displayed at any given point in time. While prior research has investigated third-party tracking in the smart TV ecosystem, it has not looked into second-party ACR tracking that is directly conducted by the smart TV platform. In this work, we conduct a black-box audit of ACR network traffic between ACR clients on the smart TV and ACR servers. We use our auditing approach to systematically investigate whether (1) ACR tracking is agnostic to how a user watches TV (e.g., linear vs. streaming vs. HDMI), (2) privacy controls offered by smart TVs have an impact on ACR tracking, and (3) there are any differences in ACR tracking between the UK and the US. We perform a series of experiments on two major smart TV platforms: Samsung and LG. Our results show that ACR works even when the smart TV is used as a "dumb" external display, opting-out stops network traffic to ACR servers, and there are differences in how ACR works across the UK and the US.