FVEY's are all seeing:
global SIGINT
rooted phones
compromised supply chain
own the Internet pipes
compromised computers
direct feeds from social media platforms
direct feeds from Internet search platforms
direct feeds from Internet apps at GOOG, M$, etc
So don't think in terms of a single attack or moment in time. Think all coverage all of the time.
Photos of London during Fall/Winter implies that they have the goods on the meetings that happened between FBI/DOJ, Fusion GPS, MI6 elements. And many other events in the past and the now…
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