Web tracking is evolving from browser- and device-tracking to people-tracking. As Internet users are increasingly accessing the web from multiple devices this new paradigm of tracking—in most cases for purposes of advertising—is aimed at crossing the boundary between a user’s individual devices and browsers. It establishes a person-centric view of users across devices and seeks to combine the input from various data sources into individual and comprehensive user profiles. By its very nature such cross-device tracking can principally reveal a complete picture of a person and, thus, become more privacy-invasive than the siloed tracking via HTTP cookies or other traditional and more limited tracking mechanisms. This presentation will explore cross-device tracking techniques as well as their privacy implications.
Particularly, I will demonstrate a method to detect the occurrence of cross-device tracking, and, based on cross-device tracking data that collected from 126 Internet users, explore the prevalence of cross-device trackers on mobile and desktop devices. I show that the similarity of IP addresses and Internet history for a user’s devices in the dataset gives rise to a matching rate of F-1 = 0.91 for connecting a mobile to a desktop device. This finding is especially noteworthy in light of the increase in learning power that cross-device companies may achieve by leveraging Internet history from more than one device. Given these privacy implications of cross-device tracking I also examine compliance with applicable self-regulation for 40 companies and find that some are not transparent about their practices.
Sebastian Zimmeck is a postdoc in computer science at Carnegie Mellon University. His research interests are web privacy and security, particularly, from a machine learning perspective. Before coming to Carnegie Mellon Sebastian studied computer science at Columbia University. He also studied information privacy and intellectual property law and practiced in these areas as an attorney with Freshfields Bruckhaus Deringer.