US National Security Agency (NSA)

America's National Security Agency (NSA) is a cryptologic intelligence agency of the United States Department of Defence responsible for the collection and analysis of foreign communications and foreign signals intelligence. The NSA is a key component of the US Intelligence community, which is headed by the Director of National Intelligence. By law, the NSA's intelligence gathering is limited to foreign communications, although there have been some incidents involving domestic collection, including the NSA warrantless surveillance controversy.