signalsintelligence

Signals intelligence, or SIGINT, is intelligence derived from the interception and analysis of electronic signals and communications. It encompasses communications intelligence (COMINT), which comes from intercepted human or machine-to-human communications, and electronic intelligence (ELINT), which relates to non-communications signals such as radar and other electronic emitters. A broader formulation sometimes includes foreign instrumentation signals (FISINT), which concerns telemetry and diagnostic data from foreign platforms. SIGINT is used to support national security, military planning, policy decisions, and law enforcement, often involving coordination across multiple agencies and, in some cases, international allies.

Historically, SIGINT emerged with the advent of wireless communications in the early 20th century and expanded dramatically during World War II and the Cold War. Developments in cryptography, signal processing, and digital communications have continually transformed the discipline, shifting from manual interception and codebreaking to large-scale automated collection, analysis, and dissemination.

Collection and processing involve a range of assets, including ground, sea, and air sensors, satellites, and network surveillance. Analysts perform traffic analysis, cryptanalysis, and content interpretation, often relying on metadata, language processing, and machine-assisted means to manage large data volumes and identify relevant targets.

Legal, ethical, and operational considerations shape SIGINT activities. Programs are governed by national laws, oversight mechanisms, and international norms, with attention to privacy, civil liberties, attribution, and the risks of misuse. Major intelligence agencies around the world conduct SIGINT and frequently participate in broader cyber and counterintelligence efforts.