There was a succession of Soviet secret police agencies over time.
 The first secret police after the October Revolution, created by Vladimir Lenin's decree on December 20, 1917, was called "Cheka" (ЧК).
 Officers were referred to as "chekists", a name that is still informally applied to people under the Federal Security Service of Russia, the KGB's successor in Russia after the dissolution of the Soviet Union.
The Organizzazione per la Vigilanza e la Repressione dell'Antifascismo (OVRA; Italian for "Organization for Vigilance and Repression of Anti-Fascism") was the secret police of the Kingdom of Italy, founded in 1927 under the regime of Fascist dictator Benito Mussolini and during the reign of King Victor Emmanuel III.
 The German Gestapo were the equivalent of the OVRA.
 Mussolini's secret police were assigned to stop any anti-Fascist activity or sentiment.
 Approximately 5,000 OVRA agents infiltrated most aspects of domestic life in Italy.
 The OVRA was headed by Arturo Bocchini.
The Gulag (Russian: ГУЛАГ ; ] ; acronym of Главное Управление Лагерей , "Glavnoye Upravleniye Lagerej ", "Main Camps' Administration" or "Chief Administration of Corrective Labor Camps") was the government agency created under Vladimir Lenin which reached its peak as the Soviet forced labor camp system during Joseph Stalin's rule from the 1930s up until the 1950s.
 The term is also commonly used to reference any forced-labor camp in the Soviet Union, including in post-Stalin times.
 The camps housed a wide range of convicts, from petty criminals to political prisoners. Large numbers were convicted by simplified procedures, such as NKVD troikas (secret police) and other instruments of extrajudicial punishment.
 The Gulag is recognized as a major instrument of political repression in the Soviet Union.
Chekism (from "Cheka", the first Soviet secret police organization) is a term to describe the situation in the Soviet Union where the secret political police controlled everything in society.It is also used by critics of the current Kremlin authorities to describe the power enjoyed by law-enforcement agencies in contemporary Russia.
The State Protection Authority (Hungarian: "Államvédelmi Hatóság" or "ÁVH") was the secret police of Hungary from 1945 until 1956.
 It was conceived as an external appendage of the Soviet Union's secret police forces and gained an indigenous reputation for brutality during a series of purges beginning in 1948, intensifying in 1949 and ending in 1953.
 In 1953 Joseph Stalin died, and Imre Nagy (a moderate reformer) was appointed Prime Minister of Hungary.
 Under Nagy's first government from 1953 to 1955, the ÁVH was gradually reined in.
The term secret police or covert police force refers to intelligence services or police and law enforcement agencies which engage in covert, domestic law enforcement, intelligence, and counter-intelligence operations.
 The level of oversight with which they are governed varies by country and political system.
 Secret police organizations are often used by totalitarian states to protect the political power of an individual dictator or an authoritarian political regime by means of systematic engagement in extrajudicial activities.
 Secret police organisations are often utilised for the purposes of policing the activities of dissidents, and weakening opposition organisations.
The KGB, an initialism for Komitet Gosudarstvennoy Bezopasnosti (Russian: "Комите́т Госуда́рственной Безопа́сности" ("КГБ") ; ] ), translated in English as Committee for State Security, was the main security agency for the Soviet Union from 1954 until its break-up in 1991, as a direct successor of such preceding agencies as Cheka, NKGB, NKVD and MGB, a committee was attached to the Council of Ministers.
 It was the chief government agency of "union-republican jurisdiction", acting as internal security, intelligence and secret police.
 Similar agencies were constituted in each of the republics of the Soviet Union aside from Russia, and consisted of many ministries, state committees and state commissions.
Joseph Vissarionovich Stalin (18 December 1878 – 5 March 1953) was a Georgian-born Soviet revolutionary and political leader.
 Governing the Soviet Union as its dictator from the mid-1920s until his death in 1953, he served as General Secretary of the Central Committee of the Communist Party of the Soviet Union from 1922 to 1952 and as Premier of the Soviet Union from 1941 to 1953.
 Ideologically a Marxist and a Leninist, Stalin helped to formalise these ideas as Marxism–Leninism while his own policies became known as Stalinism.
Yakov Khristoforovich Peters (Latvian: "Jēkabs Peterss" , Russian: Я́ков Христофо́рович Пе́терс , English: Jacob Peters, Jan Peters ; 3 December [O.S. 21 November] 1886 – 25 April 1938) was a Latvian Communist revolutionary who played a part in the establishment of the Soviet Union.
 Together with Felix Dzerzhinsky, he was one of the founders and chiefs of the Cheka ("VChK"), the secret police of the Soviet Union.
 He was the Deputy Chairman of the Cheka from 1918 and briefly the acting Chairman of the Cheka from 7 July to 22 August 1918.
Stanislav Frantsevich Redens (Russian: Станислав Францевич Реденс , Polish: "Stanisław Redens" ; May 17, 1892 – January 21, 1940) was a Soviet secret police official, one of those responsible for conducting mass repressions under Joseph Stalin.
 Redens was himself executed in 1940, after being arrested at the end of the Great Purge in 1938.

Question: Which Soviet Union dictator did secret police officer Stainslav Redens work for?
Answer: Joseph Stalin