SIGINT (Signals Intelligence)

Definition

Signals Intelligence (SIGINT) is intelligence derived from the interception and analysis of electronic signals, encompassing communications intelligence (COMINT) — intercepted messages and conversations — and electronic intelligence (ELINT) — data from non-communication electronic emissions such as radar systems. SIGINT is a dominant collection discipline for technologically advanced nations and has been central to national security since World War II code-breaking efforts. Modern SIGINT involves intercepting satellite communications, fiber-optic cables, cellular networks, and internet traffic. The NSA, GCHQ, and their Five Eyes partners operate the world's most extensive SIGINT infrastructure. SIGINT's scale and intrusiveness have raised significant privacy and civil liberties concerns.