Mole (espionage) facts for kids
The spy is recruited before having access to secret intelligence. Later, if he gets into the target organization, he or she becomes active.
However, it is popularly used to mean any long-term clandestine spy or informer in an organization, government or private. In police work, a mole is an undercover law-enforcement agent who joins an organization in order to collect incriminating evidence about its operations, and so bring its members to justice.
Mole (espionage) Facts for Kids. Kiddle Encyclopedia.