Terrorist groups use violence and threats of violence to publicise their causes and as a means to achieve their goals. They often aim to influence or exert pressure on governments and government policies but reject democratic processes, or even democracy itself.
International terrorism from groups such as the Islamic State in Iraq and the Levant (ISIL) and Al Qaida present a threat from many others. They hold territory in places without functioning governments, making it easier for them to train recruits and plan complex, sophisticated attacks. Drawing on extreme interpretations of Islam to justify their actions, these groups often have the desire and capability to direct terrorist attacks against the West, and to inspire those already living there to carry out attacks of their own.
Northern Ireland-related terrorism continues to pose a serious threat to British interests. Although the Provisional Irish Republican Army (PIRA) has ceased its terrorist campaign and is now committed to the political process, some dissident republican groups continue to mount terrorist attacks, primarily against the security forces.
Domestic extremism mainly refers to individuals or groups that carry out criminal acts in pursuit of a larger agenda, such as "right-wing extremists". They may seek to change legislation or influence domestic policy and try to achieve this outside of the normal democratic process.
MI5 has countered terrorist threats to UK interests, both at home and overseas, since the 1960s and the threat has developed significantly since then. It's challenging to understand the intentions and activities of secretive and sometimes highly organised groups. New and changing technologies make it increasingly difficult to obtain information necessary to disrupt the attack planning of these groups. Many are based in inaccessible areas overseas and there are limits to what can be done to prevent attacks planned and launched from abroad. Our techniques and the way we with work with other agencies both at home and abroad have to keep pace with the terrorists' capabilities.