The Nigerian Security Organization (NSO) was the state security and intelligence service of the Nigerian government from 1976 to 1985.
Established in 1976 by the Military regime of Olusegun Obasanjo after the failed Dimka coup--which claimed the life of former Head of State Murtala Mohammed, the NSO was given a mandate of coordinating both domestic and foreign intelligence. During the time of the military regime, and continuing through the Nigerian Second Republic, the NSO was accused of carrying out systematic and widespread human rights abuses, especially of those seen to be critical of the government. One dissident has called them a "Gestapo in Black". 
The NSO became particularly notorious during Buhari's so called War Against Indiscipline crackdown in spring 1984. A series of repressive measures, led by NSO chief Mohammed Rafindadi,  was carried out. Of these, repression against journalists, opposition figures, government officials (the Foreign Ministry saw a purge of those considered "disloyal") and the a 25 month imprisonment of musician Fela Ransome-Kuti are especially remembered.
Following the 1985 military coup that brought Ibrahim Babangida to power, the NSO was dissolved into three separate divisions per the provisions made in Decree 19:
- State Security Service (SSS) - Responsible for domestic intelligence
- Nigerian Intelligence Agency (NIA) - Responsible for Foreign intelligence and counterintelligence operations
- Defence Intelligence Agency (DIA) - Responsible for both military intelligence.
Babangida sought to clean up the reputation of the intelligence services with Decree 19, but there remains a great deal of continuity between the NSO and the SSS. In fact, the first chief of the DIA was Mohammed Rafindadi's predecessor as head of the NSO, General Aliyu Gusau.
While the NSO is reviled in modern Nigeria, many of its practices have resurfaced in the SSS, which remains directly controlled by the President, and has been accused of human rights violations. 
- Human rights in Nigeria
- Nigerian Mobile Police
- State Security Service (SSS)
- Nigerian Intelligence Agency (NIA)
- ↑ *New York Times. TOPICS; LOST IN AFRICA, January 13th, 1985.
- ↑ Nigeria Striking a Delicate Balance by John Moody. Time Magazine, Monday, Feb. 17, 1986.
- ↑ Library of Congress Country Studies. Nigeria: Return to Military Rule. and Nigeria profile.
- ↑ A fact trumpeted in the literature of Gusau's recent campaign for president, along with the suggestion that the NSO played some role in the coup.
- ↑ Reporters Without Borders: Nigeria, State Security Service (SSS).
- Intelligence profile : Nigeria. in Sixty-third edition of the N&O column / Spooks newsletter, Date: Sat, 02 Aug 2003
- Larry Diamond. Nigeria Update, in Foreign Affairs, Winter 1985/86.
- New York Times. TOPICS; LOST IN AFRICA, January 13th, 1985.
- Nosakhare Igbinosa: SSS has power of arrest. The Vanguard, February 18, 2005.