Privacy implications of presence sharing in mobile messaging applications

Mobile messaging applications, such as WhatsApp, provide a free alternative for mobile texting on smartphones. Mobile messengers typically also share presence information about users to indicate when a user is online. We investigated the privacy implications of such presence updates, using WhatsApp as an example. We conducted a user study with two independent groups (19 participants in total), in which we collected and analyzed their presence information over four weeks of regular WhatsApp use and conducted follow-up interviews. Our results show that presence information alone is sufficient to accurately identify, for example, daily routines, deviations, times of inappropriate mobile messaging, or conversation partners. We discuss resulting privacy implications of presence information and potential solutions to mitigate these issues