A group of researchers found out how to determine the location of users of messengers WhatsApp, Signal and Threema, if you organize a specially created time-based attack.

The accuracy of location detection was more than 80%.

During the attack, the attacker can be guided by notifications about the status of message delivery to the victim. They have certain predictable delays depending on user geo-position.

They can be measured "at the beginning" by sending a message when the target's location is known. The attacker can then figure out where the recipient will be next by sending a new message and measuring the time until the delivery notification is received.