From my own inquiries on the subject, I’ve learned that MAINWAY’s content is segregated by country and topic. It is the largest metadata repository in the NSA’s arsenal. Numbers and records associated with U.S. persons are treated specially. Access to that compartmentalized portion of the database is audited in real-time. Every analyst who accesses the MAINWAY telephone records to query a U.S. person’s telephone number is flagged. Determining the virtual owners of email addresses is harder. Analysts might use Google, or Lexus-Nexus, or other public tools, to try and see if a suspect email is associated with a U.S. citizen…

Let’s say that the NSA has placed a collection device like a Stingray on a cell phone tower near the home of a known trafficker in nuclear components. That device, in conjunction with a satellite or a relay system, records all of the digital data associated with all incoming cell calls, as well as the calls itself. If that proliferator calls a telephone number in the U.S., one of three things can happen:

1. If the number called is a number for which the NSA has already gotten a court order to intercept, then the analyst can listen in on the call.

2. If the number is unknown to the analyst, he or she will use a variety of tools and databases to try and identify it. If the name (if there IS a name) that comes up at the end of THIS search is the target of an ongoing FISA order, then the analyst can continue to listen.

3. If the number is identified as belonging to a U.S. person who has heretofore never been identified with nuclear proliferation or anything else, then the analyst must electronically minimize the U.S. portion of the call. Sometimes, depending on who is doing the analysis, a computer will do this before the analyst has any say in the matter.