NSA stands for National Security Agency, which is part of the U.S. Department of Defense. Its main tasks are to ensure American security and to obtain information that America's enemies wish to keep secret. It is one of the largest U.S. intelligence agencies in terms of budget.
Two primary tasks of the National Security Agency are known formally as SIGNIT and information assurance. The NSA was established by President Harry Truman in 1952, after the enormous success of the U.S. Armed Forces in breaking Japanese and German codes during World War II. The agency has been a matter of political controversy since its inception.