The National Security Agency (NSA) is a national-level intelligence agency of the United States Department of Defense, under the authority of the Director of National Intelligence. The NSA is responsible for global monitoring, collection, and processing of information and data for foreign and domestic intelligence and counterintelligence purposes, specializing in a discipline known as signals intelligence (SIGINT) . The NSA provides foreign signals intelligence (SIGINT) to the US policymakers and military forces, which plays a vital role in national security by providing critical information to defend the country, save lives, and advance US goals and alliances globally. The NSA also invests in a world-class workforce and partnerships with academia and industry to deliver capabilities that secure the nations future.

The NSAs mission, as set forth in Executive Order 12333 in 1981, is to collect information that constitutes "foreign intelligence or counterintelligence" while not "acquiring information concerning the domestic activities of United States persons". The NSA has declared that it relies on the FBI to collect information on foreign intelligence activities within the borders of the United States, while confining its own activities within the United States to the embassies and missions of foreign nations.

The NSA is also tasked with the protection of US computer networks from cyber-terrorism, and as part of the National Security Presidential Directive 54/Homeland Security Presidential Directive 23 (NSPD 54), signed on January 8, 2008, by President Bush, the NSA became the lead agency to monitor and protect all of the federal governments computer networks.

In summary, the NSA is a US intelligence agency responsible for global monitoring, collection, and processing of information and data for foreign and domestic intelligence and counterintelligence purposes, specializing in signals intelligence (SIGINT) . The agency invests in a world-class workforce and partnerships with academia and industry to deliver capabilities that secure the nations future.