Signals Intelligence
Intelligence gathered by intercepting and analyzing electronic communications, radar signals, and other electromagnetic transmissions rather than human sources.
Intelligence obtained by intercepting, processing, and analyzing electronic signals—including radio communications, radar, satellite transmissions, and other electromagnetic data. Distinct from human intelligence (spying), signals intelligence relies on technical collection methods and is a core component of modern military and national security operations.
What this means in real life
A military detects an enemy's radio chatter about troop movements, or an intelligence agency intercepts encrypted phone calls to identify a terrorist network's plans—both are signals intelligence in action.
What it isn’t
It is not the same as reading stolen documents or debriefing human informants. Signals intelligence focuses on intercepting live electronic transmissions, not physical intelligence or human sources.
Commonly misused online
Often conflated with 'mass surveillance' or 'spying on civilians.' While signals intelligence can involve civilian communications, it is a technical discipline with specific military and national-security applications, not synonymous with general eavesdropping.