Editing Counterintelligence (section)

=== Offensive counterintelligence operations ===
Wisner emphasized his own, and Dulles', views that the best defense against foreign attacks on, or infiltration of, intelligence services is active measures against those hostile services.<ref name=Wisner /> This is often called '''counterespionage''': measures taken to detect enemy espionage or physical attacks against friendly intelligence services, prevent damage and information loss, and, where possible, to turn the attempt back against its originator. Counterespionage goes beyond being reactive and actively tries to subvert hostile intelligence service, by recruiting agents in the foreign service, by discrediting personnel actually loyal to their own service, and taking away resources that would be useful to the hostile service. All of these actions apply to non-national threats as well as to national organizations.

If the hostile action is in one's own country or in a friendly one with co-operating police, the hostile agents may be arrested, or, if diplomats, declared [[persona non grata]]. From the perspective of one's own intelligence service, exploiting the situation to the advantage of one's side is usually preferable to arrest or actions that might result in the death of the threat. The intelligence priority sometimes comes into conflict with the instincts of one's own law enforcement organizations, especially when the foreign threat combines foreign personnel with citizens of one's country.

In some circumstances, arrest may be a first step in which the prisoner is given the choice of co-operating or facing severe consequence up to and including a death sentence for espionage. Co-operation may consist of telling all one knows about the other service but preferably actively assisting in deceptive actions against the hostile service.