The National Security Agency was originally founded by President Harry S. Truman in 1952, in the early days of the Cold War. The organization is designed to protect the US by gathering information about potential foreign threats through various means, as well as by protecting sensitive information about the US from foreign powers.
Even during the Cold War, the NSA was involved in some controversial activities. For example, they initiated a program which involved spying on a number of US citizens who were known to be against the war (notably including Martin Luther King Jr.), which was later revealed to have been illegal according to US law.
After 9/11, the NSA greatly expanded its abilities to monitor suspicious activities - especially its powers to monitor the internet and wiretap telephone conversations. The Patriot Act of 2002 further helped secure the legal basis for these new extensive activities, as it widened the potential scope of the NSA's surveillance - and in some contexts enabled them to monitor people who were not suspected of anything specific.
Edward Snowden (b. 1983) is a computer specialist who has worked for both the CIA and the NSA. In 2013, Snowden left his NSA job and boarded a flight to Hong Kong. While in Hong Kong, he leake...