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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 is also tasked with the
protection of U.S. communications networks and information systems. The NSA relies on a variety of measures to accomplish its mission, the majority of which are
clandestine.
The
Black Chamber (1919–1929), also known as the
Cipher Bureau, was the United States' first peacetime
cryptanalytic organization, and a forerunner of the
National Security Agency. The only prior codes and cypher organizations maintained by the US government had been some intermittent, and always abandoned, attempts by Armed Forces branches prior to WW1.
Having originated as a unit to decipher coded communications in
WW1, the NSA was officially formed by President
Harry S. Truman in 1952. Since then, it has become the
largest of the U.S. intelligence organizations in terms of personnel and budget. The NSA currently conducts
worldwide mass data collection and has been known to physically
bug electronic systems as one method to this end. The NSA is also alleged to have been behind such
attack software as
Stuxnet, which severely damaged Iran's nuclear program. The NSA, alongside the
Central Intelligence Agency (CIA), maintains a physical presence in many countries across the globe; the CIA/NSA joint
Special Collection Service (a highly classified intelligence team) inserts eavesdropping devices in high value targets (such as presidential palaces or embassies). SCS collection tactics allegedly encompass "close surveillance, burglary, wiretapping, [and] breaking and entering".
Unlike the
CIA and the
Defense Intelligence Agency (
DIA), both of which specialize primarily in
foreign human espionage, the NSA does not publicly conduct human-source intelligence gathering. The NSA is entrusted with providing assistance to, and the coordination of, SIGINT elements for other government organizations – which are prevented by law from engaging in such activities on their own. As part of these responsibilities, the agency has a co-located organization called the
Central Security Service (
CSS), which facilitates cooperation between the NSA and other U.S. defense
cryptanalysis components. To further ensure streamlined communication between the signals
intelligence community divisions, the
NSA Director simultaneously serves as the Commander of the
United States Cyber Command and as Chief of the Central Security Service.
The NSA's actions have been a matter of
political controversy on several occasions, including
its spying on anti–Vietnam War leaders and the agency's participation in
economic espionage. In 2013, the NSA had many of its secret surveillance programs
revealed to the public by
Edward Snowden, a former NSA contractor. According to the leaked documents, the NSA intercepts and stores the communications of over a billion people worldwide, including United States citizens. The documents also revealed the NSA tracks hundreds of millions of people's movements using cellphones'
metadata. Internationally, research has pointed to the NSA's ability to surveil the domestic Internet traffic of foreign countries through "
boomerang routing".
