Anyone can track WhatsApp and Signal users' activity, knowing only their phone number: "Careless Whisper: Exploiting Silent Delivery Receipts to Monitor Users on Mobile Instant Messengers"
Anyone can track WhatsApp and Signal users' activity, knowing only their phone number: "Careless Whisper: Exploiting Silent Delivery Receipts to Monitor Users on Mobile Instant Messengers"
arxiv.org
Careless Whisper: Exploiting Silent Delivery Receipts to Monitor Users on Mobile Instant Messengers
This is a year-old paper but now there is an easy-to-use implementation of the attack: https://github.com/gommzystudio/device-activity-tracker
Signal developers' verdict is WONTFIX: https://github.com/signalapp/Signal-Android/pull/14463