Our mobile phones can reveal a lot about ourselves: where we live and work; who our family, friends and acquaintances are; how (and even what) we communicate with them; and our personal habits.

The research that we and our colleagues are doing identifies and explores a significant threat that most people miss: More than 70 percent of smartphone apps are reporting personal data to third-party tracking companies like Google Analytics, the Facebook Graph API or Crashlytics.

We found that more than 70 percent of the apps we studied connected to at least one tracker, and 15 percent of them connected to five or more trackers. One in every four trackers harvested at least one unique device identifier, such as the phone number or its device-specific unique 15-digit IMEI number.

– Narseo Vallina-Rodriguez & Srikanth Sundaresan in The Conversation May 30, 2017