NSA claims secret surveillance programs have foiled at least 50 terror plots since the September 11 attacks

Head of NSA defends monitoring as legal, closely supervised and crucial to defending Americans, adding it was not “some rogue operation”

In the first public hearing dedicated to the NSA’s top-secret spying operations since former contractor Edward Snowden exposed them, General Keith Alexander defended the monitoring as legal, closely supervised and crucial to defending Americans, adding it was not “some rogue operation” (AP)

The head of the US National Security Agency has claimed secret surveillance programs have foiled at least 50 terror plots since the September 11 attacks.

In the first public hearing dedicated to the NSA’s top-secret spying operations since former contractor Edward Snowden exposed them, General Keith Alexander defended the monitoring as legal, closely supervised and crucial to defending Americans, adding it was not “some rogue operation”.

Speaking to members of the House of Representatives Intelligence Committee, General Alexander said he felt the leaks had inflicted “irreversible and significant” damage to national security, adding “I believe it will hurt us and our allies”.

Snowden's disclosures have ignited political furore over the balance between privacy rights and national security, but President Barack Obama and congressional leaders in both parties have backed the programs and no significant effort has emerged to roll them back.

Instead, during the meeting, both US officials and lawmakers spent hours justifying phone and Internet monitoring programs as vital security tools and criticised Snowden's decision to leak documents about them to media outlets.

While critics have blasted the surveillance as government overreach without enough independent oversight, proposed legislative remedies discussed so far have focused on tightening rules for contractors and making the secret court that approves warrants for surveillance more transparent.

General Alexander told Congress: “I would much rather be here today debating this point than trying to explain how we failed to prevent another 9/11.”

He added: “In recent years these programs, together with other intelligence, have protected the US and our allies from terrorist threats across the globe to include helping prevent... potential terrorist events over 50 times since 9/11“.

Alexander said at least 10 of those plots involved US targets or suspects in the United States, and promised to give classified details of all of the foiled incidents to the House and Senate intelligence committees within 24 hours.

US Representative Mike Rogers, the Republican chairman of the intelligence panel, told reporters after the hearing: “People who are sceptical of the program have no understanding of what the program is”.

Sean Joyce, deputy FBI director, offered information on two of the cases - a plot to bomb the New York Stock Exchange and a conspiracy to give money to a Somali militia designated by the United States as a terrorist group.

Last week officials revealed two other such potential attacks: a 2009 plan to bomb a Danish newspaper that published cartoons of the Prophet Mohammad and a plot by Islamist militants to bomb the New York subway the same year.

Members of the intelligence committee said they were holding the hearing to set the record straight about how the programs operated and their importance for national security.

Representative Dutch Ruppersberger, the panel's top Democrat, said the leaks “put our country and our allies in danger by giving the terrorists a really good look at the playbook that w use to protect our country. The terrorists now know many of our sources and methods.”

Snowden, who worked at an NSA facility in Hawaii for 15 months, defended his actions in an web chat on Monday and vowed to release more details on the extent of the agency's access. Snowden is believed to be hiding in Hong Kong as the US Justice Department conducts a criminal investigation.

Asked what was next for Snowden, Joyce gave a one-word response: “Justice.”

Alexander said he had “significant concerns” about how a low-level contractor like Snowden could gain access to so much information and said it was part of the FBI's investigation. “We do have significant concerns in this area and it is something that we need to look at,” he said.

He said the NSA was considering starting a “two-person control” system in which no one could download sensitive data without a second person there to approve it.