During my career I signed dozens of NDAs. They were all either umbrella or caveat specific. All of them cited Title 18 referencing punishments (including death) for violations of the NDA, and all of them were related to either Title 10 or Title 50 activities.

Without being too specific, what I observed was the use of NSA assets to surveil grow operations within the US. It was explained to me that it began with Ronald Reagan's War On Drugs.

I've seen much worse since then while supporting Waived / Unacknowledged programs. Present classification requirements dictate that those be reviewed for declassification after 40 years, but they will never see the light of day because all documentation is destroyed at the end of the program and not archived anywhere.