internet data really necessary to keep the country safe? >> the information gathered from these programs provided the u.s. government with critical leads to help prevent over 50 potential terrorist events in more than 20 countries. >> what is less clear is whether these specific programs now in the news were themselves crucial to breaking up the plots? >> reporter: the nsa tried to offer some details on terror plots it says would not have been uncovered solely with traditional law enforcement. in the matter of najibullah zazi. >> the zazi plots were intercepted as a result of an e-mail sent by an al qaeda operative in pakistan to zazi in denver, colorado. before that e-mail was sent, the united states had no idea a plot was in the works to attack new york. >> reporter: case number two, the u.s. monitored an extremist