In the previous posting we saw that the domestic telephone records, which NSA collected under authority of Section 215 of the USA PATRIOT Act (internally referred to as BR-FISA), were stored in the centralized contact chaining system MAINWAY, which also contains all kinds of metadata collected overseas.
Here we will take a step-for-step look at what NSA analysts do with these data in order to find yet unknown conspirators of foreign terrorist organisations.
It becomes clear that the initial contact chaining is followed by various analysis methods, and that the domestic metadata are largely integrated with the foreign ones, something NSA never talked about and which only very few observers noticed.
What is described here is the situation until the end of 2015. The current practice under the USA FREEDOM Act differs in various ways. The information in this article is almost completely derived from documents declassified by the US government, but these have various parts redacted.