Signals intelligence

Signals intelligence (SIGINT) is the practice of intercepting, decoding, and analyzing electronic communications and emissions to extract information of military, political, or economic value. It encompasses communications intelligence (COMINT), which targets the content of messages, and electronic intelligence (ELINT), which analyzes the characteristics of signals themselves — frequencies, modulations, and source locations — without necessarily decoding content. The National Security Agency is the world's largest SIGINT organization, operating a global collection apparatus that intercepts telephone, internet, and satellite traffic at scale. SIGINT is not merely a technical discipline; it is a structural force in international relations, shaping what states know about each other and what they can credibly threaten. The tension between SIGINT collection and the protection of civilian communications is the defining conflict of modern cryptographic politics.