The KGB (Komitet Gosudarstvennoi Bezopasnosti or Committee of State Security) was the preeminent Soviet intelligence agency and Soviet equivalent of the American CIA.
During the later Soviet period, the KGB served as organization primarily responsible intelligence and counterintelligence matters. Although the NKVD was tasked with internal security, the KBG role in political security and counterintelligence was so broad that its operations often touched on internal security matters. Even Soviet border guards were eventually placed under KGB supervision.
The head of the KGB enjoyed an important position in the totalitarian regime hierarchy. In 1967, Andropov, then head of KGB and later Soviet premier, described the role of the KGB and other state security bodes as engaged in "a bitter and stubborn battle on all fronts, economic, political, and ideological.
The KGB and Western intelligence services played a continual deadly game of "cat and mouse" (both as pursuers and the pursued) throughout the Cold War. KGB officers and operatives played an important role in the attempt to overthrow the government of the first (and last) president of the USSR, Mikhail Gorbachev and was essentially abolished or devolved into successor agencies after the failure of the anti-Gorbachev putsch and the collapse of the USSR in 1991.
The KGB's culture continue to heavily influence Russian politics and policy. After the fall of the Soviet Union, former KGB officer Vladimir Vladimirovich Putin, became President of the successor, Russian Federation. Moreover, the following Russian Federation agencies were created from within the KGB: the Federal Security Service (FSB); the Federal Agency of Government Intercommunication, which is responsible for communications between top state officials; the Guard Service, which guards top state officials; and the Outer Intelligence Service, which collects and processes all data coming from abroad.
Some of the bizarre disinformation created by the KGB and regurgitated anti-U.S. critics, still survives as urban myth or folk legend. For example, documents in the KGB archives now provide evidence that KGB operatives mounted a disinformation campaign laden with pseudo scientific "proofs" and language that was designed to influence third-world nations that the United States had deliberately created the AIDS virus in the laboratory to use as a biological weapon. (more)
[Author's note: in 2016 U.S. intelligence agencies, including the CIA, NSA, and DIA united in approving an Intelligence Community Assessment (ICA) concluding that "Russia, like its Soviet predecessor, has a history of conducting covert influence campaigns focused on U.S. presidential elections" including the 2016 U.S. Presidential Campaign. The ICA conclusion -- based on evidence known by 29 December 2016 and offered with generally high confidence was that Russian hacking, along with propaganda and disinformation efforts (including the creation and dissemination of fake news), were undertaken with the direct knowledge and approval of Russian President Vladimir Putin and other senior Russian officials. Read more at https://www.academia.edu/30817272/_The_Bear_Gets_a_BOGO_The_ICA_on_Russian_Meddling_in_the_2016_U.S._Presidential_Election]