John McMurtrie: In “The Shadow Factory,” you wrote that the NSA’s watch list — “of people, both American and foreign, thought to pose a danger to the country” — once had only 20 names on it, then rose to “an astonishing half a million.” Do you know what the figure is now?

James Bamford: The Terrorist Identities Datamart Environment list, known as TIDE, now contains about 875,000 names.

Q: PRISM has reportedly given the NSA access to exabytes of confidential data. To give readers some perspective, roughly how much information is contained in an exabyte? How many books could fit in one?

A: An exabyte is about 960,767,920,505,705 pages of text or about 4,803,839,602,528 books containing 200 pages.

Q: Privacy concerns aside, one of the problems with collecting all this data, you have written, is that “the NSA is akin to Jorge Luis Borges’s “Library of Babel,” a place where the collection of information is both infinite and at the same time monstrous, where the entire world’s knowledge is stored, but not a single word understood.” What does the NSA need to do to make practical use of this data?

A: The problem is the bigger you build the haystack, the harder it is to find the needle. Thus, despite all this collection, the NSA missed the Boston bombing, the underwear bomber and the Times Square bomber. And most, if not all, of the “successes” they point to could have been discovered using much less invasive surveillance. [Continue reading…]