WhatsApp flaw may reveal when a user is talking to someone else

A potential design flaw has been found in WhatsApp that will let anyone to track a user's activity. It can also be exploited to spy on a user’s sleeping patterns – the time you go to bed and wake up.
 
After discovering the flaw in WhatsApp, Rob Heaton, who has also made similar security-related findings in the past, stated on his website that one can track you by your ‘last seen’ and ‘online’ status feature. With this vulnerability, a hacker can potentially check up on a user’s activity anytime. The code could even be tweaked to correlate more than two people messaging each other.
 
Unfortunately, there is nothing you can do to stop attackers from monitoring your activity. While the app has an option to show your last seen status to everyone, only your contacts, or no one, there is no way to disable the online status feature which reveals when you are actively using the service. This data can be easily collected on a mass level and then sold to third-party firms for advertising purposes.

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