Messenger apps show your friends’ online status. Anytime you open the app, they’ll notify the service that you’re “online” at the moment. Now everybody else can see it in their contact lists.
And with everybody I mean anybody! If you have a phone number you can check that person’s online status as often as you want from wherever you want (no need to be friends or anything).
So did a group of researchers at the Friedrich-Alexander-Universität Erlangen-Nürnberg. They used this “feature” to “find out how frequently and how long users spent with their popular messenger” on a random sample of 1000 people in different countries for over eight months.
Looking through the project’s website should make it clear how little the creators of those apps care …
Moreover, we were able to run our monitoring solution against the WhatsApp services from July 2013 to April 2014 without any interruption. Although we monitored personal information of thousands of users for several months — and thus strongly deviated from normal user behaviour — our monitoring efforts were not inhibited in any way.
… and that they don’t want you to be able to care.
Unfortunately, affected messenger services (like WhatsApp, Telegram, etc.) currently provide no option for disabling access to a user’s “online” status. Even WhatsApp’s newly introduced privacy controls fail to prevent online status tracking, as users still cannot opt-out of disclosing their availability to anonymous parties.