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Information on the protective security measures that can achieve the protective security principles of Deter, Detect, Delay, Mitigate and Response at the perimeter. 

Last Updated 18 March 2021


Perimeter covers:

  • The line demarcating the extent of a site/building/asset often using a physical barrier
  • Access points within the demarcation line providing a means of entering/exiting for people or vehicles
  • Sterile zones consisting of two perimeter lines separated by an area of ground; the outer (attack side) perimeter is a sacrificial fence facilitating detection and the inner (defended side) perimeter provides delay



  • Dissuade adversaries from conducting an attack by making each element within the boundary line appear too physically/technically difficult to overcome without likelihood of detection/failure/capture


  • Install a security rated fence and commensurately rated portals around the site, which combined with appropriate signs emphasises the strength of the security measures. The number of portals should be kept to an absolute minimum
  • Introduce random, visible security patrols around the site
  • Utilise signage on a sacrificial fence line highlighting the use of CCTV cameras and security lighting


  • To identify suspicious behaviour at the perimeter boundary
  • To identify unauthorised intrusions across the boundary line
  • To raise an alarm and initiate further investigation
  • Verify all perimeter intrusion alerts
  • Initiate an appropriate response to a threat or attack as early as possible
  • Enable verification of attack force size/threat/direction of travel to the responding security team


  • Install a perimeter intrusion detection system and CCTV camera system capable of detecting and tracking an intrusion at all times of the day and night
  • Use fixed and pan-tilt-zoom cameras along with lighting to detect an intruder and track their direction of travel once inside the perimeter


  • Maximising the time taken for an attack to breach the perimeter once detection has taken place
  • Prevent an attack from breaching the perimeter


  • Install an approved security barrier and portal which maximises delay
  • Install approved hostile vehicle mitigation measures around the perimeter


  • Use of perimeter protection measures to minimise the impact of an attack whilst considering the potential of the security equipment to add to the effects of an attack
  • Maximise the protection provided  at access points at the perimeter


  • Consider the materials perimeter protective measures are constructed from (eg glass) to ensure materials selected minimise additional injury (eg laminated glass)
  • Locate screening facilities in areas where the effects of an attack will be contained and limited


  • Determine what responses are required at your perimeter for the range of threats that your site faces and ensure measures are tied into response
  • Where appropriate, exercise your response plans involving all relevant internal and external stakeholders
  • Consider the ability of a response force to access an incident, including where the incident has affected access points


  • Use of perimeter detection system to determine an attack is taking place and its location, and the use of standard operating procedures to deploy an internal security team to investigate
  • Incident response plans which include the use of multiple entry points to a range of incidents

The following pages provide more information on the protective security measures which can be used to achieve the protective security principles above. Considering the impact a measure has on Deter, Detect and Delay is important to ensure the measures are complementary and all three Ds have been covered.

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