Apps, Trackers, Privacy, and Regulators: A Global Study of the Mobile Tracking Ecosystem.

Third-party services form an integral part of the mobile ecosystem: they ease application development and enable features such as analytics, social network integration, and app monetization through ads. However, aided by the general opacity of mobile systems, such services are also largely invisible to users. This has negative consequences for user privacy as third-party services can potentially track users without their consent, even across multiple applications. Using real-world mobile traffic data gathered by the Lumen Privacy Monitor (Lumen), a privacy enhancing app with the ability to analyze network traffic on mobile devices in user space, we present insights into the mobile advertising and tracking ecosystem and its stakeholders. In this study, we develop automated methods to detect third-party advertising and tracking services at the traffic level. Using this technique we identify 2,121 such services, of which 233 were previously unknown to other popular advertising and tracking blacklists. We then uncover the business relationships between the providers of these services and characterize them by their prevalence in the mobile and Web ecosystem. Our analysis of the privacy policies of the largest advertising and tracking service providers shows that sharing harvested data with subsidiaries and third-party affiliates is the norm. Finally, we seek to identify the services likely to be most impacted by privacy regulations such as the European General Data Protection Regulation (GDPR) and ePrivacy directives.