Who Knows What About Me? A Survey of Behind the Scenes Personal Data Sharing to Third Parties by Mobile Apps

What types of user data are mobile apps sending to third parties? We chose 110 of the most popular free mobile apps as of June-July 2014 from the Google Play Store and Apple App Store, across 9 categories likely to handle potentially sensitive data about users including job information, medical data, and location. For each app, we used a man-in-the-middle proxy to record HTTP and HTTPS traffic that occurred while using the app and looked for transmissions that include personally identifiable information (PII), behavior data such as search terms, and location data, including geo-coordinates. An app that collects these data types may not need to notify the user in current permissions systems.