What is signals intelligence and who is charged with providing it?

The intelligence discipline – and the U.S. Intelligence Community – requires a very broad range of activity, from tasking, to collection, to processing. Within the collection slice of that intel pie, there are many and varied sub-disciplines also referred to as the INTs. One of them is signals intelligence, or SIGINT.

The Department of Defense defines SIGINT as, “A category of intelligence comprising either individually or in combination all communications intelligence (COMINT), electronic intelligence (ELINT), and foreign instrumentation signals intelligence (FISINT), however transmitted,” as well as, “Intelligence derived from communications, electronic, and foreign instrumentation signals.”

SIGINT is a pretty broad field (with several sub-fields) in an already very broad field: Although DoD lists three subdisciplines of SIGINT, there are more, (like Traffic Analysis and Electronic Order of Battle, or EOB). But beneath all the fancy definitions, SIGINT is intelligence collection through the interception of signals – whether those signals are via communications (COMINT) or electronic signals (ELINT).

SIGINT is also highly dependent on and involved with encryption, therefore it is tightly linked to cryptography and cryptanalysis.

The disciplines of cryptography and cryptanalysis are two sides of the same coin: one encodes and the other decodes, respectively. The overall importance of those two disciplines far exceeds their application to things like intelligence collection or national security. Nowadays, almost anything that involves the coded sequence of ones and zeros jumps through one hoop or the other to a certain degree.

Related: How American spies helped the UK retake the Falklands

Those responsible for collecting SIGINT

Within the United States Intelligence Community, there are several organizations, units, and platforms that provide SIGINT capabilities. The most notable, of course, is the National Security Agency, or NSA. Yet every branch of the military provides many levels of SIGINT capability, operation, and support. From strategic levels, which directly support the NSA and national policy objectives, to highly tactical elements and “frontline” units such as the Marine Corps’ Radio Reconnaissance Platoons or the Army Special Forces’ SOT-As. SIGINT trickles as far down as brigade combat teams and maneuver battalions and SIGINT troops and systems exist for direct support.

Other SIGINT platforms include such diverse systems as the now-infamous ECHELON global network, airborne Guardrail and Rivet Joint aircraft, various drones like Predators and Reapers, and even “spy ships” sporting systems like the AN/SLQ-32 electronic warfare suite.

When someone says that military intelligence is the “eyes and ears of the commander,” SIGINT is absolutely the ears.

Editor’s Note: This article was originally published in October 2021. It has been edited for republication.

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