Inside The US Intelligence Community Edward Snowden Has Exposed

The U.S. intelligence community is vast, composed of 17 distinct organizations each operating under its own shroud of secrecy.

Oversight of these agencies generally falls to the Department of Defense or Congress, leaving the average citizen with precious little knowledge of how they operate.

Before ex-NSA contractor Edward Snowden's leaks, we knew very little about their budget, mission, or capabilities. 

Now, months after he first went public in June, and after a number of top-secret disclosures, we know much more.

This is what we know so far about the secretive U.S. intelligence community.

The Central Intelligence Agency spies on foreign governments and organizes covert ops.

The CIA is the most well-known U.S. spying agency, formed by the passage of the National Security Act of 1947. The agency has its roots with the Office of Strategic Services (OSS) that operated during World War II.

Headquarters: Langley, Va.

Mission: CIA collects, analyzes, and disseminates intelligence gathered on foreign nations. This comes through signals and human intelligence sources.

Budget: $14.7 billion. They are the biggest spenders in the spy community, accounting for 28% of the total intelligence community budget.

Employees: 21,459 full-time equivalent civilian employees.

The National Security Agency was once so secretive it was jokingly called 'No Such Agency.'

The NSA was established in 1952 with a mission primarily dedicated to code breaking, after the Allies' success in cracking German and Japanese codes during World War II. For a long time, the NSA, which operates under the Dept. of Defense, was not even recognized by the government, commonly referred to as "No Such Agency."

Headquarters: Fort Meade, Md.

Mission: The main functions of the NSA are signals intelligence (SIGINT) — intercepting and processing foreign communications, cryptology — cracking codes, and information assurance. IA is, put simply: preventing foreign hackers from getting secret information.

Budget: $10.8 billion.

Employees: Nearly 35,000 (includes code-breaking components of the military services as well).

The Defense Intelligence Agency works to understand what foreign militaries will do before they do it.

The DIA was established in 1961 with the goal of sharing information collected by the major military intelligence outfits (such as Army or Marine Corps Intelligence). More recently, the DIA has been expanding its overseas spy network to collect first-hand intelligence.

Headquarters: Washington, D.C.

Mission: The DIA serves as the lead intelligence agency for the Dept. of Defense, coordinating analysis and collection of intelligence on foreign militaries, in addition to surveillance and reconnaissance operations. The DIA is the common link between military and national intelligence agencies.

Budget: $4.4 billion.

Employees: 16,500.