What term describes intelligence derived from electromagnetic communications systems by non-intended recipients?

The term that describes intelligence derived from electromagnetic communications systems by non-intended recipients is Communication Intelligence, often abbreviated as COMINT. This type of intelligence specifically pertains to the interception and analysis of communications between individuals or groups, typically conducted through radio, telephone, or other forms of electronic communication.

COMINT focuses on the content of communications, allowing analysts to derive meaning from transmitted messages that were not intended for their reception. This can include anything from extracting strategic insights to understanding adversarial intentions based on their communication patterns.

The other terms provided, while related to electronic warfare and intelligence gathering, serve different purposes. Electronic Warfare Support (ES) refers to actions taken to exploit and gather information on enemy electromagnetic activity. Direction Finding (DF) involves pinpointing the location of a signal source rather than analyzing the content of communication itself. Electronic Intelligence (ELINT) pertains to the collection and analysis of electronic signals not used for communication, such as radar emissions. Thus, COMINT is the most accurate term for the process of obtaining intelligence from intercepted communications systems.