A measurement study of tracking in paid mobile applications

Smartphone usage is tightly coupled with the use of apps that can be either free or paid. Numerous studies have investigated the tracking libraries associated with free apps. Only a limited number of these have focused on paid apps. As expected, these investigations indicate that tracking is happening to a lesser extent in paid apps, yet there is no conclusive evidence. This paper provides the first large-scale study of paid apps. We analyse top paid apps obtained from four different countries: Australia, Brazil, Germany, and US, and quantify the level of tracking taking place in paid apps in comparison to free apps. Our analysis shows that 60% of the paid apps are connected to trackers that collect personal information compared to 85%--95% in free apps. We further show that approximately 20% of the paid apps are connected to more than three trackers. With tracking being pervasive in both free and paid apps, we then quantify the aggregated privacy leakages associated with individual users. Using the data of user installed apps of over 300 smartphone users, we show that 50% of the users are exposed to more than 25 trackers which can result in significant leakages of privacy.