A look at some key U.S. government agencies in the intelligence-gathering business:
Central Intelligence Agency
The main goal of the CIA is to collect, analyze, evaluate and disseminate foreign intelligence to help government leaders make decisions related to national security. The agency collects information through technological and human sources and sometimes undertakes covert actions at the direction of the president.
National Security Agency
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The NSA is responsible for protecting the government's information system and producing foreign signals intelligence information. The NSA has experts in analyzing code, mathematics, computer science and foreign language.
National Reconnaissance Office
The NRO is responsible for designing, building and operating reconnaissance satellites. Data collected are used to warn of potential foreign military aggression, to monitor weapons of mass destruction programs, enforce arms control and environmental treaties, and assess the impact of natural and manmade disasters.
National Geospatial-Intelligence Agency
The NGA collects and creates intelligence and data about the Earth for navigation purposes, national security, military operations and humanitarian aid efforts.
Defense Intelligence Agency
The mission of the DIA is to "provide timely, objective and cogent military intelligence to warfighters, defense planners and defense and national security policymakers." The DIA assesses foreign militaries, focusing on weapons of mass destruction, missile systems, terrorism and defense-related medical issues.
Bureau of Intelligence and Research
The INR, a division of the State Department, provides analysis of global developments to the State Department. The bureau is the secretary of state's principal adviser on all intelligence matters.
Federal Bureau of Investigation
The FBI is responsible not only for law enforcement but for understanding threats to our national security. The agency coordinates efforts to penetrate those groups that have the ability to harm the United States, focusing on terrorist organizations, foreign intelligence services and criminal groups.
Department of Homeland Security
Homeland Security is charged with ensuring that state and local law enforcement officials receive federal intelligence on terrorist threats.
The agency assesses intelligence on worldwide nuclear terrorism threats, nuclear proliferation and evaluates foreign technology threats.
The treasury collects intelligence that could affect U.S. fiscal and monetary policies. It also monitors terrorist financing.
Drug Enforcement Administration
The DEA enforces controlled substances laws and regulations and provides drug-related information to the intelligence communities.
U.S. Coast Guard
A division of the Department of Homeland Security, the Coast Guard protects and monitors port security, search and rescue, maritime safety, counternarcotics and alien migration.
Each branch of the military -- the Army, Navy, Air Force and Marines -- also have their own intelligence operations, bringing the total number of agencies to 16.