double agent

A double agent is a person who works simultaneously for two opposing intelligence services or parties to a conflict, typically by passing information to both sides. The defining characteristic is the deliberate dual role: outwardly the person appears to be a loyal member of one service, while secretly reporting to an opposing service.

Kim Philby is history's best-known example. As a senior officer in the British intelligence service MI6 — and at one point head of MI6's counter-espionage section — he systematically passed classified information to the Soviet intelligence service KGB. He had been recruited as a Soviet agent as early as the 1930s and remained operational for decades before fleeing to Moscow in 1963.

Under Danish law, 'double agent' does not exist as an independent criminal designation. The relevant legislation is the Danish Penal Code (straffeloven) § 107, which concerns espionage against the Danish state, together with § 108, which criminalises assisting a foreign intelligence service. A double agent's actions will typically fall under one or both of these provisions, depending on what information has been passed on and to whom.

The term is used primarily as a descriptive one in intelligence and journalistic contexts. It differs from a simple spy precisely in the double aspect: the person holds a genuine, trust-based position with the party being betrayed, which makes detection particularly difficult and the damage particularly extensive.