RAY SUAREZ:

The tool at issue is the national security letter. It's been used for more than three decades by the FBI to obtain sensitive information about businesses and individuals.

Approved by Congress after the 9/11 attacks, the USA Patriot Act extended the bureau's access to telephone, e-mail, library and financial records in suspected terrorism investigations without court approval. More than 150,000 national security letters have been issued over the last three years, compared with just 8,000 the year before 9/11.

Today, Director Mueller underscored how important the Patriot Act and the national security letters in particular can be to the war on terror.