FBI Director Robert S. Mueller III has admitted that the FBI used shortcuts, violated internal policies, and improperly used “exigent circumstances letters” and “national security letters” to gather information through its counterterrorism powers under the Patriot Act.

Exigent circumstances letters and national security letters are methods for making emergency demands for personal information from telephone companies, internet service providers, banks, credit bureaus, and other organizations. Review of their use has uncovered instances of false and undocumented evidence being used to connect the records sought to ongoing espionage or counterterrorism investigations, among other improper practices.

Source: http://www.washingtonpost.com/wp-dyn/content/article/2007/03/17/AR2007031701451.html?sub%3DAR&sub=new