Towards Understanding the Advertiser´s Perspective of Smartphone User Privacy

Many smartphone apps routinely gather various private user data and send them to advertisers. Despite recent study on protection mechanisms and analysis on apps´ behavior, the understanding about the consequences of such privacy losses remains limited. In this paper we investigate how much an advertiser can infer about users´ social and community relationships by combining data from multiple applications and across many users. After one month´s user study involving about 200 most popular Android apps, we find that an advertiser can infer 90% of the social relationships. We further propose a privacy leakage inference framework and use real mobility traces and Foursquare data to quantify the consequences of privacy leakage. We find that achieving 90% inference accuracy of the social and community relationships requires merely 3 weeks´ user data. The discoveries underscore the importance of early adoption of privacy protection mechanisms.