Informants with the slang, background story, paperwork and history that was created and correct for a group, cult, political event or other gathering.
Creating informants. Disrupting any real gatherings and recreating the members in a new front group as bait.
Computer networks attract like minded people to post and chat about their interests. At that stage their anonymity and privacy is fair game.
Encryption will not protect the origin of the message from a domestic system like Tempora
https://en.wikipedia.org/wiki/...
Privacy is gone when interacting with over time with interesting, creative strangers.
Encryption protects the message along the network. If the end site is a trap or has malware? The users origin could be traced with creative code on a site.
Keep a person of interest posting, making friends, invite them to help with very simple admin work. Turn them, track them or just use their content as bait.
Thats why encryption never worried the NSA or GCHQ. The encryption sold or offered was a junk standard or the entire surrounding network was tame.
The origins or and color of law that followed the The Communications Assistance for Law Enforcement Act (CALEA)
https://en.wikipedia.org/wiki/... should allow some insight into the tame networks.