The 5 D’s of Perimeter Security: the Ultimate Guide

A security guardattending a security barrier at the entrance of a manufacturing site

Whether for manned or unmanned remote sites, perimeter security is about creating an effective physical barrier which can detect, deter, delay and deny unauthorized access to the perimeter and ultimately defend the asset.


Outdoor perimeter security is often overlooked, taking a back seat to interior measures which are often much more costly. Why is this?

When a small investment in outdoor security (e.g. static manned guarding provisions) can provide significant protection to your building’s assets as they add distance, time, and scale to your security plan, why are we spending most of our budget on our interior security? Doesn’t this sound like we’re counting on potential criminals gaining access to our premises? Shouldn’t we be investing in measures to prevent access as much as possible first before implementing these interior measures as our ‘just in case’ security?

5 D’s of Perimeter Security (‘The Onion Principle’)

In a solid security plan, security is thought of in layers. This is where the onion comes in.

Thinking about the layers of a business and working from the outside into the centre, a security plan should have many layers (or barriers) which the potential criminal has to overcome, each one getting stronger the closer you get to the centre to provide greater protection to the target (your interior assets).

A warning security sign

From this idea, you can see that outdoor preventative measures are a pivotal element in making sure that a security strategy is as impenetrable as it possibly can be. What’s more is that, if designed correctly, your outdoor measures can actually reduce the cost of your building security!

To implement a foolproof security strategy in your business, you need to design it around the layers of your business using the 5 D’s of perimeter security.

1. Deter

The first layer (or barrier) of your business is the farthest one from the location of your assets so the strength of these measures aren’t as much of a concern; the aim of these measures are just to deter the criminal from attempting a crime in the first place. From CCTV signs to fences and security lighting, these deterrents can cause a psychological battle within the potential criminal so that criminal activity never starts.

2. Detect

If the first layer fails to deter criminal activity, your next layer (detection) should alert you to any possible unauthorised breaches; the aim of these measures is to allow you to respond as efficiently and effectively as possible. Surveillance camera technology, motion sensors, and alarms are very effective detection tools with megapixel cameras being among the most accurate.

Security man looking at surveillance camera footage

3. Deny

Although the criminal may have made it through your first layer of defence, your second layer has alerted you so that you can keep the unauthorized persons out with your third layer; the aim at this stage is to deny unauthorised access while allowing authorised persons to enter the premises. Whether you have a manned security gate or access control technology at the point of entry of your business, you can use both to deny this specific entry.

4. Delay

You have probably alerted the police by this point, so the objective in your fourth layer is to delay or slow down the intrusion long enough that the security team can respond or that the intruder gives up. Delay security measures include more fences, gates, and locked windows and doors, however, surveillance cameras should also be used here to provide situational awareness and measure the effectiveness of the measures.

A man trying to break a locked gate

5. Defend

If the intruder isn’t giving up and looks like they might make it through your fourth layer, your final layer is to defend your perimeter; the aim here is for your security to apprehend the intruder and to escort them off your premises. Again, surveillance should be used to record the situation and determine the effectiveness of the response. This final perimeter often includes the involvement of law enforcement but this often overlaps with other layers depending on your security strategy.

Your outdoor perimeter security is absolutely essential to creating a strong and effective security strategy. Not only does it contribute greatly to a foolproof design, but it can also reduce the overall cost of your security system. Sounds like a win-win to us!

What we can do for you:

RGM Security offers a wide range of security services as well as penetration testing to check your defences and threat awareness training for your staff.  If you need training or just advice, please don’t hesitate to contact us!

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