How does the National Security Agency collect signals intelligence?

The National Security Agency (NSA) collects signals intelligence (SIGINT) by intercepting, processing, and analyzing foreign electronic communications and signals. As the world’s largest collector of such intelligence, the agency operates global interception posts and conducts research into all forms of electronic transmissions.12

The NSA’s collection efforts generally fall into three categories:

• Communications Intelligence: Intercepting foreign communications not intended for the agency, which helps reveal enemy strategies and weaknesses.1
• Electronics Intelligence (ELINT): Analyzing electromagnetic emissions from foreign weapons or electronic systems to determine their purpose.1
• Telemetry Intelligence: Intercepting and analyzing data from foreign sources, such as signals emitted during ballistic missile tests, to assess weapon capabilities like range and accuracy.1

The agency also utilizes advanced surveillance programs to monitor Internet service providers and collect metadata from cellular phone calls, text messages, and location data. While the Foreign Intelligence Surveillance Act restricts the targeting of U.S. citizens, the agency maintains a broad mandate to monitor foreign communications critical to national security.2