There was also a more secretive body called the Citizens Defence Force, responsible directly to Kevin O’Higgins and funded through the offices of Arthur Cox.
A study of the period concluded, 'Oriel House succeeded in its task of suppressing small scale republican activities in the Dublin area, not by the sophistication and efficiency its intelligence work... but by the more direct method of striking terror into its opponents.
[6] They were disbanded after the Civil War: supposedly because of squeamishness on the part of Kevin O’Higgins; but a core was retained as G-division of the Dublin Metropolitan Police: the G-men, headed by ex-RIC Inspector David Neligan.
[8] All government ministers and former Presidents and Taoisigh are provided with armed protection and transport when their security is deemed under threat, otherwise it is reserved for official state occasions.
The SDU uses anti-terrorism legislation (chiefly the Offences against the State Acts) to conduct operations, and uses the non-jury Special Criminal Court to prosecute terrorism offenders.
The SDU is a highly secretive organisation that does its utmost to stay out of the media spotlight, and when officers from the unit appear in court they routinely give evidence anonymously from behind a screen to protect their identity.
The fund used to pay informers is known as the "Secret Service" budget, and it is shared between the Crime & Security Branch and Directorate of Military Intelligence.
The Special Detective Unit works with the National Economic Crime Bureau (GNECB) in relation to financial intelligence and terrorism financing.
The SDU has historically operated in tandem with American, British and other European law enforcement agencies in combating terrorists and foreign government threats.
[24][25] In 2010, the Special Detective Unit, Garda Bureau of Fraud Investigation (GBFI) and Criminal Assets Bureau (CAB) broke up what was described by Europol as "one of the biggest and most sophisticated counterfeiting operations ever uncovered in Europe", which had the capacity to produce €200 million (£167 million/$276 million) in counterfeit banknotes annually, some of which were shipped as far away as Japan, in an attempt to fund IRA terrorist and criminal activities.
[26] The Special Detective Unit was the principal security agency involved in protecting Britain's Queen Elizabeth II on her historic visit to Ireland in the summer of 2011, facing a significant threat from dissident republican paramilitary organizations, and they prevented a number of attempted bombings and assassination attempts to ensure a peaceful visit.
[27][28] The SDU also worked alongside the United States Secret Service (USSS) and Diplomatic Security Service (DSS) in a heightened security state during the visit of US President Barack Obama to Ireland in 2011, fearing retaliation from al-Qaeda terrorists in response to the death of Osama bin Laden a number of weeks earlier.
[29] Following the outbreak of the Syrian Civil War (2011–present) and the campaign of violence perpetrated by the "Islamic State" (2014) terrorist organisation in Iraq, the Middle Eastern Bureau of the Special Detective Unit and the Directorate of Military Intelligence increased their monitoring of Irish residents and citizens who travelled to conflict regions in the Middle East to partake in fighting, with the fear they may become radicalised and carry out Islamic jihadist terrorist attacks in Ireland, Europe and North America upon their return.
[30] The Middle Eastern Bureau and Military Intelligence is tasked with monitoring between 30 and 60 people living in Ireland who are under suspicion due to their links with Muslim extremist organisations.
[31][32] The Irish authorities have been working with the British security services, MI5 and the Secret Intelligence Service (SIS/MI6), to identify possible returning terrorists by sharing data, information and intelligence, operating a joint database and watchlist, and cross-checking airline passenger manifests to track Irish and UK residents and citizens who are travelling to and from conflict zones in the Middle East.
A number of journalists have accused the unit of monitoring their electronic communications, as well as carrying out covert surveillance on them when they are meeting sources in person.
Some journalists allege they have been questioned (and threatened with arrest) about sources used in crime and terrorism stories, including about Garda officers speaking to the media when not sanctioned to do so by senior management.