防諜
攻撃的カウンターインテリジェンスの作戦の類型 > 二重スパイ > 多様に転身する諜報員

A triple agent can be a double agent that decides his true loyalty is to his original service, or could always have been loyal to his service but is part of an active provocation of your service. If managing a double agent is hard, agents that turned again (i.e., tripled) or another time after that are far more difficult, but in some rare cases, worthwhile.
Any service B controlling, or believing it controls, a double agent, must constantly evaluate the information that agent is providing on service A. While service A may have been willing to sacrifice meaningful information, or even other human assets, to help an intended penetration agent establish his bona fides, at some point, service A may start providing useless or misleading information as part of the goal of service A. In the World War II Double Cross System, another way the British controllers (i.e., service B in this example) kept the Nazis believing in their agent, was that the British let true information flow, but too late for the Germans to act on it. The double agent might send information indicating that a lucrative target was in range of a German submarine, but, by the time the information reaches the Germans, they confirm the report was true because the ship is now docked in a safe port that would have been a logical destination on the course reported by the agent. While the Double Cross System actively handled the double agent, the information sent to the Germans was part of the overall Operation Bodyguard deception program of the London Controlling Section. Bodyguard was meant to convince the Germans that the Allies planned their main invasion at one of several places, none of which were Normandy. As long as the Germans found those deceptions credible, which they did, they reinforced the other locations. Even when the large landings came at Normandy, deception operations continued, convincing the Germans that Operation Neptune at Normandy was a feint, so that they held back their strategic reserves. By the time it became apparent that Normandy was indeed the main invasions, the strategic reserves had been under heavy air attack, and the lodgment was sufficiently strong that the reduced reserves could not push it back.
There are other benefits to analyzing the exchange of information between the double agent and his original service, such as learning the priorities of service A through the information requests they are sending to an individual they believe is working for them. If the requests all turn out to be for information that service B could not use against A, and this becomes a pattern, service A may have realized their agent has been turned.
Since maintaining control over double agents is tricky at best, it is not hard to see how problematic this methodology can become. The potential for multiple turnings of agents and perhaps worse, the turning of one’s own intelligence officers (especially those working within counterintelligence itself), poses a serious risk to any intelligence service wishing to employ these techniques. This may be the reason that triple-agent operations appear not to have been undertaken by U.S. counterintelligence in some espionage cases that have come to light in recent years, particularly among those involving high-level penetrations. Although the arrest and prosecution of Aldrich Ames of the CIA and Robert Hanssen of the FBI, both of whom were senior counterintelligence officers in their respective agencies who volunteered to spy for the Russians, hardly qualifies as conclusive evidence that triple-agent operations were not attempted throughout the community writ large, these two cases suggest that neutralization operations may be the preferred method of handling adversary double agent operations vice the more aggressive exploitation of these potential triple-agent sources.
Triple agent
A concern with triple agents, of course, is if they have changed loyalties twice, why not a third or even more times? Consider a variant where the agent remains fundamentally loyal to B
Quadruple agent
Successes such as the British Double Cross System or the German Operation North Pole show that these types of operations are indeed feasible. Therefore, despite the obviously very risky and extremely complex nature of double agent operations, the potentially quite lucrative intelligence windfall – the disruption or deception of an adversary service – makes them an inseparable component of exploitation operations.
If a double agent wants to come home to Service A, how can he offer a better way to redeem himself than recruiting the Service B case officer that was running his double agent case, essentially redoubling the direction of the operation? If the case officer refuses, that is apt to be the end of the operation. If the attempt fails, of course, the whole operation has to be terminated. A creative agent can tell his case office, even if he had not been tripled, that he had been loyal all along, and the case officer would, at best, be revealed as a fool.
Occasionally a service runs a double agent whom it knows to be under the control of the other service and therefore has little ability to manipulate or even one who it knows has been successfully redoubled. The question why a service sometimes does this is a valid one. One reason for us is humanitarian: when the other service has gained physical control of the agent by apprehending him in a denied area, we often continue the operation even though we know that he has been doubled back because we want to keep him alive if we can>.
Another reason might be a desire to determine how the other service conducts its double agent operations or what it uses for operational build-up or deception material and from what level it is disseminated. There might be other advantages, such as deceiving the opposition as to the service's own capabilities, skills, intentions, etc. Perhaps the service might want to continue running the known redoubled agent in order to conceal other operations. It might want to tie up the facilities of the opposition. It might use the redoubled agent as an adjunct in a provocation being run against the opposition elsewhere.
Running a known redoubled agent is like playing poker against a professional who has marked the cards but who presumably is unaware that you can read the backs as well as he can.
アフガニスタンのシール・アリー・ハーン国王と彼の「友人」であるロシアの熊とイギリスのライオンを描いた政治的戯画（1878年）。グレート・ゲームでは両国による組織的なスパイ活動と監視がこの地域全体で行われた。
オフラーナは1880年に創設され、敵のスパイ活動を取り締まる任務を担った。1905年、サンクトペテルブルクでの集合写真。