He was appointed to the IRA's Internal Security Unit and liaised between Northern Command and rural units in Tyrone and Armagh.
Internal Revenue Service | Central processing unit | Law & Order: Special Victims Unit | National Security Agency | The Unit | National Security Council | Organization for Security and Co-operation in Europe | United States National Security Council | United Nations Security Council | National Security Advisor | United States Department of Homeland Security | security | Internal Revenue Code | National Security Advisor (United States) | Social Security Administration | United Nations Security Council resolution | Larissa (regional unit) | United Nations Security Council Resolution 1267 | Transportation Security Administration | Hacker (computer security) | George C. Marshall European Center for Security Studies | Economist Intelligence Unit | Diesel multiple unit | United Nations Security Council Resolution 1373 | Internal combustion engine | central processing unit | Transport Layer Security | Social Security | Internal medicine | Company (military unit) |
The most senior alleged informer in the Belfast IRA was Freddie Scappaticci, who was the head of the IRA's Internal Security Unit from 1980 to 1990.