Covert operation

A covert operation is a military operation intended to conceal the identity of (or allow plausible denial by) the operation. Covert operations should not be confused with clandestine operations, which are performed in secret.
Covert operations aim to secretly fulfill their mission objectives without anyone knowing who sponsored or carried out the operation, or in some cases, without anyone knowing that the operation has even occurred. 
Impact.
According to a 2018 study by University of Chicago politician scientist Austin Carson, covert operations may have the beneficial effect of preventing escalation of disputes into full-blown wars. He argues that keeping military operations secret can limit escalation dynamics, as well as insulate leaders from domestic pressures while simultaneously allowing them communicating their interest to the adversary in keeping a war contained. He finds that covert operations are frequently detected by other major powers.
Laws.
Under U.S. law, the Central Intelligence Agency (CIA) must lead covert operations unless the president finds that another agency should do so and properly informs Congress. Normally, the CIA is the U.S. government agency legally allowed to carry out covert action. The CIA's authority to conduct covert action comes from the National Security Act of 1947. President Ronald Reagan issued Executive Order 12333 titled "United States Intelligence Activities" in 1984. This order defined covert action as "special activities", both political and military, that the US Government could legally deny. The CIA was also designated as the sole authority under the 1991 Intelligence Authorization Act and in Title 50 of the United States Code Section 413(e). The CIA must have a "Presidential Finding" issued by the President of the United States in order to conduct these activities under the Hughes-Ryan amendment to the 1991 Intelligence Authorization Act. These findings are then monitored by the oversight committees in both the U.S. Senate and the House of Representatives. As a result of this framework, the CIA "receives more oversight from the Congress than any other agency in the federal government". The Special Activities Division (SAD) is a division of the CIA's Directorate of Operations, responsible for Covert Action and "Special Activities". These special activities include covert political influence and paramilitary operations.
Military intelligence and foreign policy.
Covert operations and clandestine operations are distinct. The "Department of Defense Dictionary of Military and Associated Terms" (Joint Publication JP1-02), defines "covert operation" as "an operation that is so planned and executed as to conceal the identity of or permit plausible denial by the sponsor. A covert operation differs from a clandestine operation in that emphasis is placed on concealment of a sponsor rather than on concealment of the operation". The United States Department of Defense definition has been used by the United States and NATO since World War II.
In a covert operation, the identity of the sponsor is concealed, while in a clandestine operation the operation itself is concealed. Put differently, "clandestine" means "hidden", while "covert" means "deniable". The term "stealth" refers both to a broad set of tactics aimed at providing and preserving the element of surprise and reducing enemy resistance and to a set of technologies (stealth technology) to aid in those tactics. While secrecy and stealthiness are often desired in clandestine and covert operations, the terms "secret" and "stealthy" are not used to formally describe types of missions.
Covert operations are employed in situations where openly operating against a target would be disadvantageous. Operations may be directed at or conducted with allies and friends to secure their support for controversial components of foreign policy throughout the world. Covert operations may include sabotage, assassinations, support for coups d'état, or support for subversion. Tactics include the use of a false flag or front group.
The activity of organizations engaged in covert operations is in some instances similar to or overlaps with, the activity of front organizations. While covert organizations are generally of a more official military or paramilitary nature, like the DVS German Air Transport School in the Nazi era, the line between both becomes muddled in the case of front organizations engaged in terrorist activities and organized crime.
Law enforcement.
Undercover operations (such as sting operations or infiltration of organized crime groups) are conducted by law enforcement agencies to deter and detect crime and to gather information for future arrest and prosecution.
In popular culture.
Covert operations have often been the subject of popular films ("Zero Dark Thirty", "Argo", "The Falcon and The Snowman", "The Kremlin Letter"), novels, TV series, and comics.
The Company is a fictional covert organization featured in the American TV series "Prison Break". Also other series that deal with covert operations are "", "Alias", "Burn Notice", "The Unit", "The State Within", "Covert Affairs", "Air Wolf", "24", "The West Wing", "The Blacklist", "Scandal, Strike Back series, and Vagabond."