Read about the Dulles brothers. They forged very strong connections between overt and covert foreign policy and industry.
The book does veer somewhat into unfounded conspiracy territory, but I think it's an interesting read so far and the author doesn't come across as crazy so much as skeptical.
And there is the essence of why we want transparency, oversight, restricted privacy etc. I generally feel that if everything the security services did was publically available (at least on level with civilian police) there would be a lot of friction but they would get immersurably better.