General Michael Flynn was really big on a kind of OSINT approach which devalued the current crop of experts in Washington, before he got railroaded out of the National Security Establishment in 2014-2015 (no comment on his later political antics). Basically he said for any information produced by a spy, you could have found the exact same info in some tiny circulation magazine or journal available for free, if only someone had been there to read it in whatever language to read / report it.