The main threats to national security are terrorism, espionage, and cyber attacks. Understanding the threat facing us is key to ensuring protective security measures and mitigations are proportionate, effective and responsive.

  • contact 999 to report an imminent threat
  • contact the Anti-Terrorist Hotline on 0800 789 321, or your local police on 101 to report suspicious activity.

You can also report in confidence online via the Action Counters Terrorism website.


1. UK national threat levels

There are 5 types of UK national threat levels: Critical, Severe, Substantial, Moderate and Low.

Terrorism threat levels are designed to provide a broad indication of the likelihood of a terrorist attack. They are based on the assessment of a range of factors including current intelligence, recent events and what is known about terrorist intentions and capabilities. Those who own, operate, manage or work in crowded places are reminded that Substantial and Severe threat levels indicate a high level of threat and that an attack might well come without warning.

Information about the national threat level is available on our page about Threat Levels.


2. Building response levels

There are 3 types of building response level: Exceptional, Heightened and Normal.

Building response levels provide a general indication of the protective security measures that should be applied at a given time. They are informed by the UK national threat level, but also take into account specific assessments of vulnerability and risk.

Building response levels relate to the UK national threat levels and tend to apply to sites, whereas the UK national threat levels usually relate to broad areas of activity. There are a variety of site-specific security measures that can be applied in each building response level, although the same measures will not necessarily be found at every location.

The security measures deployed at different response levels should not be made public to avoid informing terrorists about what we know and what we are doing about it.


3. Threat and response level definitions

To support your planning, the UK national threat level and building response levels are combined within the below table:

threat level

4. Action to be considered now

  • carry out a risk assessment specific to your site or venue

  • identify a range of practical protective security measures appropriate for each of the building response levels. Consider the different attack types – your local CTSA can assist 

  • regularly review the building response level for your site or venue

  • clearly display signage informing staff of the building response level. This should not be displayed in public areas or within their sight

  • regularly train, test and exercise your protective security measures

The protective security measures to be implemented at each building response level are a matter for individual premises or organisations and will differ according to a range of circumstances. All protective security measures should be identified in advance of any change in threat and building response levels and should be clearly notified to those staff who are responsible for ensuring compliance. It is important to test and exercise your activity for each response level.

Read the National Stakeholder Menu of Tactical Options for further advice on improving your security stance during a heightened UK national threat level.

PALs Guidance
publicly accessible locations
ProtectUK publication date