The Directorate for Investigations had agents and informants placed in virtually every echelon of the party and government, as well as among the public, to report on the antiregime activities and opinions of ordinary citizens. It perpetrated illegal entries into public offices and private homes and interrogated and arrested people opposed to Ceausescu's rule. Its agents frequently used force to make dissidents provide information on their compatriots and their activities. According to some prominent dissidents, because of the directorate's influence over judges and prosecutors, no dissident arrested by it had ever been acquitted in court. It worked closely with the Directorate for Surveillance and the Directorate for Mail Censorship. The latter monitored the correspondence of dissidents and ethnic Hungarians in Transylvania. Toward this end, it collected handwriting samples from the population and supervised the official registration of all typewriters and copying machines by the police. The General Directorate for Technical Operations (Directia Generala de Tehnica Operativa--DGTO) was an integral part of the Securitate's activities. Established with the assistance of the KGB in the mid-1950s, the DGTO monitored all voice and electronic communications in the country. The DGTO intercepted all telephone, telegraph, and telex communications coming into and going out of the country. It secretly implanted microphones in public buildings and private residences to record ordinary conversations among citizens.

The Directorate for Counterespionage conducted surveillance against foreigners Soviet nationals in particular to monitor or impede their contacts with Romanians. It enforced a variety of restrictions preventing foreigners from residing with ordinary citizens, keeping them from gaining access to foreign embassy compounds and requesting asylum, and requiring them to report any contact with foreigners to the Securitate within twenty-four hours. Directorate IV was responsible for similar counterespionage functions within the armed forces, and its primary mission was identifying and neutralizing Soviet penetrations. Directorate V and the Directorate for Internal Security focused mainly on party and government leadership cadres. Directorate V provided protective services and physical security for Romanian officials. With more than 1,000 agents, the Directorate for Internal Security concentrated on rooting out disloyalty to Ceausescu within the PCR hierarchy, the Council of Ministers, and the Securitate itself. It was a small-version Securitate in itself, with independent surveillance, mail censorship, and telephone monitoring capabilities. An additional source of information on attitudes toward the regime within the Securitate was one of Ceausescu's relatives, who was a lieutenant general in the Ministry of Interior. There were few signs of widespread organized opposition to the Ceausescu regime in the late 1980s, but scattered and sporadic indications of social and political unrest were increasing. This opposition emanated from political and human rights activists, workers, religious believers, ethnic minority groups, and even former mid-level officials of the PCR. But the ubiquitous Securitate effectively suppressed dissidence because activists were few in number and isolated from one another and from their potential followers.

The Securitate had an effective overall strategy and varied tactics for suppressing dissidence. It relied primarily on extralegal reprisals against leading individual dissidents that ranged from petty harassment, threats, and intimidation to physical beatings at the hands of the plainclothes militia. Dissidents were often fired from their jobs and then prosecuted and imprisoned for "parasitism," even though they were frequently denied all opportunities to work. To isolate dissidents from one another and from Western diplomats and media representatives inside Romania who could bring them international attention, the state denied them residence permits that were required by law before they could live in major cities. The state either avoided prosecuting dissidents in open trials that would generate publicity for their causes or prosecuted them in secret trials before military courts. Even if they avoided detention, some well-known dissidents had their telephone and mail service interrupted and were jailed without warning. Several lived under virtual house arrest and constant surveillance by plainclothes Securitate agents and the uniformed militia, who cordoned off their apartments and intimidated potential visitors. Dissidents were often vilified publicly in the media as traitors, imperialist spies, or servants of the ancient régime. When the cases of certain dissidents became known to international human rights organizations and the state was unable to act freely against them, the Securitate pressured these dissidents to emigrate by making their lives unbearable and granting them exit visas to leave the country.

In 1982 a Romanian agent who was dispatched to kill dissident writers Paul Goma and Virgil Tanase in Paris defected to French authorities before undertaking his mission. This episode severely strained previously close French-Romanian relations. The DIE's primary target abroad, however, was the Munich-based staff of Radio Free Europe's (RFE) Romanian service, many of whom were Romanian émigrés. For many years, RFE's Romanian service had monitored internal developments in Romania and exposed the repressive nature of the Ceausescu regime. The beating and stabbing of several RFE staff members by unidentified assailants, several death threats, and the deaths from cancer of three successive directors of the Romanian service were attributed by some observers to DIE operations. Also within the Directorate for Operations, Service D conducted covert operations, including the dissemination of forgeries and disinformation, to promote Romanian national interests and foreign policies. According to Pacepa, Service D's forgeries and disinformation were designed to influence Western countries to reward Romania for its independence of the Soviet Union with economic assistance and trading privileges and to generate political support among Third World countries.

Service Z of the Directorate for Operations reportedly maintained ties to non-state entities including guerrilla movements, terrorist groups, and international organized crime.

The Directorate for Technical Equipment was responsible for designing or obtaining specialized espionage equipment required by the DIE. It was reportedly involved in equipping some Romanian trucks to conduct espionage operations in Western Europe.

Ministry of National Defence

Special Telecommunications Service

Counter-intelligence Directorate

Intelligence Directorate of the Army

Ministry of Internal Affairs/Intelligence Directorate

Directorate for Military Intelligence/(Directia de Informatii a Armatei--DIA)

Ministry of Justice

General Police Inspectorate

Operative Surveillance and Intelligence Directorate