The director of the US National Security Agency, General Keith Alexander, told senators in a public hearing today that the agency "intends" within the next week to release the exact number of terror plots that were foiled by its sweeping surveillance of US phone records. The secret program, which has been collecting call data such as phone numbers and length from all Verizon customers for at least a few months, and likely customers of other carriers for years, was revealed in leaked documents published by The Guardian last week.

"I don't have those figures today."

"I don't have those figures today," Alexander said when asked point-blank by Senator Patrick Leahy (D-VT) if the NSA kept an exact account of terror plots it stopped thanks to its blanket phone records surveillance. "We're going to make those figures available," Alexander said. "Over the next week it would be our intent to get those figures out." Alexander told Leahy that he gave an "approximate number" of foiled terror plots to lawmakers during a classified hearing on Monday, but wanted to check back with the NSA and the Defense Department to ensure he could release the number publicly without compromising security. Listen to an audio clip from the hearing below, which begins with Senator Leahy's questioning.

"It's dozens of terrorist events that these have helped prevent," Alexander said, deviating considerably from his prepared testimony. Several lawmakers and US officials have said in recent days that the NSA's phone surveillance, and a separate internet surveillance program known as PRISM, were used to stop terror plots and arrest suspects, but have also declined to provide many specifics on how or why such surveillance was critical in these cases. Alexander took a similar position during the hearing, pointing back to the 2009 arrest of a suspect who was later charged with plotting to bomb the New York City subway system. The law behind the NSA's internet surveillance program, Section 702 of the Foreign Intelligence Surveillance Act (FISA), "was not just critical, but the one that developed the lead on" the 2009 terror plot, Alexander said.

"It's dozens of terrorist events that these have helped prevent."

Meanwhile, a separate law allows the NSA to surveil phone records of millions of innocent people, Section 215 of the Patriot Act, which was not invoked in the 2009 case. Nonetheless, Alexander said both of these laws contributed to the agency's ability to break up multiple terror plots in the years since the September 11th, 2001 terror attacks. "They complement each other," Alexander said. "What you're asking me to do is to state 'A or B contributed solely to that.' The reality is they work together."

"clearly this authority is being used for something other than phone records."

Other senators prodded Alexander to further explain just how much data the NSA was collecting from both phone and internet surveillance, how it handled that data, and the way it interpreted the laws that gave it these seemingly broad surveillance powers. "Last year the government filed 212 Section 215 orders," said Senator Richard Durbin (D-IL), "So clearly this authority is being used for something other than phone records." Alexander pushed back: "All we use this today is for the business records," and brought up September 11th, 2001 hijackers, saying a lack of such surveillance tools was what prevented the government from "mak[ing] those connections." Alexander said the way the NSA's phone surveillance program worked was that it put "to-from" records into a "secure environment," which it could only search after the agency obtained a court order to get specific information on a suspect.

Senators Durbin and Collins (R-ME) also brought up Edward Snowden, the admitted leaker of the NSA documents to The Guardian, asking how the NSA could allow such a young private defense contractor to have so much access to information on classified government programs. "I do have concerns over that," Alexander said, vowing to "go back and look at these processes." Collins asked about Snowden's claim that as a defense contractor, he could have accessed the phone calls or emails of virtually any American. "False, I know of no way to do that," Alexander said.