Claim: The National Security Agency is responsible for signals intelligence.

The National Security Agency -LRB- NSA -RRB- is a military intelligence organization and a constituent of the United States Department of Defense -LRB- DOD -RRB- . The NSA is responsible for global monitoring , collection , and processing of information and data for foreign intelligence and counterintelligence purposes , a discipline known as signals intelligence -LRB- SIGINT -RRB- . NSA is concurrently charged with protection of U.S. government communications and information systems against penetration and network warfare . Although many of NSA 's programs rely on `` passive '' electronic collection , the agency is authorized to accomplish its mission through active clandestine means , among which are physically bugging electronic systems and allegedly engaging in sabotage through subversive software . Moreover , NSA maintains physical presence in a large number of countries across the globe , where its Special Collection Service -LRB- SCS -RRB- inserts eavesdropping devices in difficult-to-reach places . SCS collection tactics allegedly encompass `` close surveillance , burglary , wiretapping , breaking and entering . ''   Unlike the Defense Intelligence Agency -LRB- DIA -RRB- and the Central Intelligence Agency -LRB- CIA -RRB- , both of which specialize primarily in foreign human espionage , NSA does not unilaterally conduct human-source intelligence gathering , despite often being portrayed so in popular culture . Instead , NSA is entrusted with assistance to and coordination of SIGINT elements at other government organizations , which are prevented by law from engaging in such activities without the approval of the NSA via the Defense Secretary . As part of these streamlining responsibilities , the agency has a co-located organization called the Central Security Service -LRB- CSS -RRB- , which was created to facilitate cooperation between NSA and other U.S. military cryptanalysis components . Additionally , the NSA Director simultaneously serves as the Commander of the United States Cyber Command and as Chief of the Central Security Service .   Originating as a unit to decipher coded communications in World War II , it was officially formed as the NSA by President Harry S. Truman in 1952 . Since then , it has become one of the largest U.S. intelligence organizations in terms of personnel and budget , operating as part of the Department of Defense and simultaneously reporting to the Director of National Intelligence .   NSA surveillance has been a matter of political controversy on several occasions , such as its spying on anti-Vietnam-war leaders and economic espionage . In 2013 , the extent of some of the NSA 's secret surveillance programs was revealed to the public by Edward Snowden . According to the leaked documents , the NSA intercepts the communications of over a billion people worldwide , many of whom are United States citizens , and tracks the movement of hundreds of millions of people using cellphones . Internationally , research has pointed to the NSA 's ability to surveil the domestic Internet traffic of foreign countries through `` boomerang routing '' .