I think the basic flaw here is that author assumes that NSA does data-mining. I personally doubt it.
Rather (and here I'm going off on pure speculation myself) I think they can use the system to start with some off-line lead (say one of the Chechen bomber brothers) - and see who he was calling / emailing and then checking if there is anything valuable there.
Ie - how in the past FBI would do an investigation off-line and talk to people and piece things together - they are looking to be able to replicate it (possibly by going back in time) online.
"As part of K.D.D., an algorithm was applied to the broader data set in efforts to detect patterns of behavior fitting models that had been previously established as being indicative of the activities of a terrorist cell."
Thank you. But the next sentence reads " It is also run against a large set of what are known as “dirty numbers”—telephones linked to terrorists either through American signals intelligence or information provided by foreign services. Even the Libyans under Qaddafi turned over huge stacks of dirty numbers to us."
So that seems to correlate with what I am saying - they have some flag generated offline that they use as a marker to find something online.
Rather (and here I'm going off on pure speculation myself) I think they can use the system to start with some off-line lead (say one of the Chechen bomber brothers) - and see who he was calling / emailing and then checking if there is anything valuable there.
Ie - how in the past FBI would do an investigation off-line and talk to people and piece things together - they are looking to be able to replicate it (possibly by going back in time) online.