How did I overlook Edward Snowden's revelations in light of Chelsea Manning's? Permanent Record is perhaps the most historic account on domestic U.S. surveillance in the Digital Age. Even then, Snowden shares principles that span his life so far as an all-American military kid to an American-in-exile. One of those principles, from his childhood, is the method by which he details several of the NSA's signals intelligence programs.
Disturbing they are (or were?), but I recommend you not search the Web for them until you read Permanent Record in full. As a front-end user, you might benefit from the stream of consciousness of a former back-end admin with top security clearances. Especially if you're not a technologist.
Related: "Cybersecurity and Cyberwar"
Related: International Law (2021)
Related: Computer Technology (2021)
Related: Computer Networking 2 (Notes)