Countering terrorism

What is terrorism?

Terrorists use violence and threats of violence to influence the government or an international governmental organisation, or to intimidate the public. They do this in pursuit of a political, religious, racial or ideological cause. The full definition of terrorism is set out in law and the Crown Prosecution Service offers information about terrorism offences

The terrorist threat to the UK 

The threat from terrorism has changed over time. This page explains the current terrorist threat picture and our work in response. The Joint Terrorism Analysis Centre independently assesses the terrorist threat to the UK and sets the UK’s national terrorism threat level.

MI5 is responsible for investigating all forms of terrorist threat to the UK. Primarily, this stems from Islamist terrorism, extreme right-wing terrorism, Northern Ireland-related terrorism and, to a lesser degree in terms of volume, left-wing, anarchist or single-issue terrorism. 

MI5’s role 

MI5’s role is to identify, investigate and work with partners to disrupt all forms of terrorist threat in the UK and against UK interests overseas. We do this regardless of the ideology motivating a terrorist. We have a range of powers available to us to conduct our investigations. You can find out more about these in the ‘How We Work’ section of our website. 

We work closely with lots of other partners to keep the UK safe from terrorism. In addition to our joint work with GCHQ and SIS, we work in partnership with Counter Terrorism Policing, a network of specialist police teams working around the country alongside our own regional network. In London, our counter-terrorism mission is co-located with Counter Terrorism Policing in the world-leading Counter Terrorism Operations Centre. Counter Terrorism Policing work alongside MI5 during all stages of counter terrorism investigations and are usually central to disrupting threat through arrests and criminal proceedings. In Northern Ireland, our key partner is the Police Service of Northern Ireland. 

Find out more about where we work

The UK’s overall response to the terrorist threat is published in the Government’s counter-terrorism strategy, CONTEST. 

In our work, we divide terrorist ideology into four main categories. The reality of today’s terrorist threat is fluid can mean that terrorists can be appear to be motivated by multiple, unclear or shifting ideologies rather than a singular extremist narrative. 

Terrorist ideologies

Islamist terrorism is the most significant terrorist threat to the UK by volume.

Islamist terrorists are generally driven by an extreme interpretation of Islam or perceived grievances against ‘the West’, particularly those propagated by terrorist groups such as Daesh (also referred to as ISIL, ISIS or the Islamic State) or al-Qaeda. Much of the volume of the threat is from individuals who have self-radicalised, seeking to carry out attacks using unsophisticated or low-sophistication methodologies. Generally, individuals will decide themselves to conduct an attack, rather than the attack being directed or controlled by a terrorist group. This can make it harder to identify terrorist activity. 

There also remains an enduring threat from overseas terrorist groups which seek to inspire, support or enable attacks and which retain an intent to conduct sophisticated attacks.

Northern Ireland-related terrorism continues to threaten UK interests. Some dissident republican groups continue to mount terrorist attacks, primarily against security forces but with the potential to cause harm in wider communities in Northern Ireland. 

There is a separate terrorism threat level for Northern Ireland-related terrorism in Northern Ireland, which is set by MI5. MI5 has an office in Northern Ireland.

The extreme right wing terrorism landscape has evolved away from structured groups towards a more diffuse threat where individuals form loose networks, often online. The ideologies and grievance narratives are varied, wide-ranging and often overlapping. They can encompass elements of cultural nationalism, white nationalism, and white supremacism and are often fuelled by conspiracy theories.

Extreme right-wing influencers operating globally online seek to fuel grievances and amplify conspiracy theories. Much of the volume of the threat is from self-radicalised terrorists seeking to conduct low-sophistication attacks. Generally, individuals will decide themselves to conduct an attack, rather than the attack being directed by a terrorist group. This can make it harder to identify terrorist activity.

Left-wing, anarchist and single-issue terrorism makes up a significantly smaller portion of our casework than other forms of terrorism. It encompasses a wide range of ideologies. It includes those from the extreme political left-wing as well as anarchists who seek to use violence to advance their cause in seeking to overthrow the state in all its forms.

Terrorist methodologies 

Terrorists will seek carry out attacks in a number of ways. They could look to use bladed or blunt force weapons, could seek to use vehicles as a weapon or construct and use improvised explosive devices. Terrorists will often plan their attack by visiting an attack site to conduct what is known as ‘hostile reconnaissance’. Terrorists planning attacks will often try hard to keep their activities hidden, including using encrypted messaging platforms. 

The National Protective Security Authority, which is part of MI5, provides advice and guidance about protective security measures to deter, or mitigate the impact of, a terrorist attack. 

What you can do 

If you have seen or heard something that could potentially be related to terrorism, you should trust your instincts and report it. Your actions could save lives. There is more information on how to report terrorist activity, including terrorist content you may seen online on this webpage. 

The National Protective Security Authority (NPSA) is part of MI5 and provides expert protective security advice to businesses and other organisations to help counter both terrorism and state threats. 

Visit the NPSA website

NPSA’s expertise also helps to inform the advice and information available on ProtectUK which provides business and the public with counter terrorism support and guidance to effectively protect and prepare.

Visit ProtectUK

Work in counter-terrorism

By joining MI5, you can contribute directly to countering the terrorist threat to the UK. 

We have a range of roles – from working on investigations to intelligence gathering, agent handling and more – that will put you at the cutting edge of keeping the country safe. 

Find out more about working for MI5 and as well as our current opportunities.