Apps are tracking WhatsApp users' online activity, including whom they're likely talking to and when they're sleeping

The user data that the Facebook-owned messaging app [WhatsApp] shares publicly is allowing dozens of outside apps to track aspects of WhatsApp users' online activity — including whom they're likely talking to, when they're sleeping, and when they're using their devices. 

These apps and services use the "online" signaling feature within WhatsApp to enable their users to monitor the digital habits of anyone using WhatsApp without their knowledge or consent, Business Insider has found.

These intrusive apps highlight how even services that strongly protect users' privacy in some ways — like WhatsApp's commitment to encryption — can still expose data that can be used to track their users.