IIRC
"This leads me to think that they probably had the "metadata" (i.e. they were doing real time scanning of the whatsapp network to see who is messaging who), but are unable to decipher the messages themselves."
You know, I'm fairly certain that when this mass-monitoring gig first hit the broader news, we were assured by all sorts of gov and TLA types that they only wanted the meta-data and weren't interested, or authorised, to access the actualy *content* of our communications.
Whatever happened to that undertaking?
Biting the hand that feeds IT
