general/espionage

Type of accidental phone call

Substance used for writing which is invisible and can later be made visible

Spy management

Surveillance device

Tabletop science fiction role-playing game

Act of secretly listening to the private conversation of others

Surrogate organization answering to someone else

British counter-espionage and deception operation of WW2

Method for exposing an information leak

Espionage techniques

Covert entries to gather intelligence