they have to get a national security warrant before they can get the material. this is built around process, lawyers, backstopping, awed 270 make sure everybody's doing it right. like any program, the more you have in terms of packstopping and checks and -- backstopping and checks and balances, the cleaner it will be. our able to look in on that is limited. that's why you have congressional oversight, inspector generals and so on. >> we want to talk about the potential for abuses. glen greenwald and ari fleischer in a moment. has this been used to prevent a terror attack that we know of? >> this has been used successfully in terms two of things. one, it has detected nascent plots and provided the lead material and intelligence to get in front of those plots. on a substantive level it caught a plot at the last minute and saved new york city from a series of bombings. monday, september 6, at 7:58 a.m. in 2009, as it was dawn in colorado, an e-mail went from aurora, colorado, from an apartment complex to a selector that was in pakistan. this belonged to rasheed rouff, al qaeda's master planner, bomb-maker. the e-mail said, "i'm having trouble with the recipe. i need to know how much yeast and how much flour to use." this was code for a bombmaking recipe that wasn't working for a guy named najibul azazzi.