One of their missions is infrastructure security of nationally important assets. Usually this is military stuff. But think power grids, etc… NSA ironically puts out some good security stuff. Their “manageable network plan” pdf is a must read for anyone hacking to wrangle a new environment, even if it isn’t followed by the owners of said environment.

I’ve been recommending it to various localities after my security assessments for years now. https://apps.nsa.gov/iaarchive/library/ia-guidance/security-...