What is the difference between SIGINT and COMINT?

• A. SIGINT is only about electromagnetic emissions; COMINT only about warfare operations.
• B. SIGINT and COMINT are identical.
• C. COMINT is signals intelligence overall; SIGINT is about content.
• D. SIGINT is signals intelligence overall; COMINT is a subset focusing on the content of communications.

Answer: (D)

Signals intelligence is the broad field that covers gathering intelligence from all kinds of signals and transmissions, not just one narrow type. Within that broad category, a specific focus is COMINT, which means the content of communications—what people or machines are actually saying or transmitting in voice, text, data, or other message content.

So COMINT is a part of SIGINT, a subset that concentrates on the communications themselves. That’s why the best way to describe it is that SIGINT is the overall field, and COMINT narrows in on the content of those communications.

Other options miss this relationship: SIGINT isn’t limited to just electromagnetic emissions, and COMINT isn’t about warfare operations in general. They aren’t identical, and the roles aren’t reversed—the content-focused area is the subset within the broader SIGINT domain.