Security Engineering

Perimeter Security - 1 -Layers

Defending the Perimeter - 1st Layer:

Outermost perimeter is line of demarcation.

  • Crossing the boundary establishes intent - marks an aggressor.
  • It is the first opportunity to provide detection.
  • Usually provides minimal delay.


Exclusion Zone - 2nd Layer:

Defined inner perimeter or open space.

  • Obstruction free or clear zone.
  • Allows detection of aggressors or threats.
  • Supports sensor based detection.

Traveling across intermediate space is vulnerability for aggressor and provides delay.

Building Exterior - 3rd Layer:

Depending on level of public access, building exterior may be significant layer of the protective system. It defines the end of site security. The remaining layers are defined within the building as appropriate for the assets within.

Perimeter Security - 2 - Components

2.1 Fencing

Many styles of fencing:
• Chainlink
• Ornamental
• Anti-Climb / High Security

• Most have limited ability to delay penetration
• Can be used as a platform for detection sensors
• Some can also be helpful in obscuring targets or even predetonating certain standoff weapons

2.2 Vehicle Barrier Systems

Barrier systems are used to defend against the moving vehicle bomb threat. Of Two types:
• Passive
• Active

Design is based on capacity to absorb or dissipate kinetic energy of threat vehicle allowing no more than the maximum allowed penetration. Almost all systems are tested to prove performance. You should be weary of using any product that hasn’t been tested

2.2.1 Passive Vehicle Barriers

Barrier is stationary and it is designed to prevent the vehicle from penetrating successfully past barrier.
Sometimes incorporated into perimeter barrier / fence.
Insure Containment of Unscreened or Suspect Vehicles; only permit access through access points.
Can often use topographical features as passive vehicle barriers.

2.2.2 Active Vehicle Barriers

Selection Based on Required Operational Performance and Site Conditions.

Potential Threat Must be Quantified
• Kinetic Energy - I.e. 15,000 lb vehicle at 40 mph
• Angle of Approach

Barrier is Selected such that can Absorb the Kinetic Energy While Not Allowing Penetration That Exceeds the Allowable for the Site

Perimeter Security - 3 - Tactics

3.1 Tactic: Vehicle Bombs

Stationary Vehicle Bombs:
• With stationary bombs the aggressor doesn’t attempt to crash through barriers
• Attempt to get as close the facility as possible with out risking detection
• Historically, the most common type of vehicle bomb attack

Moving Vehicle Bombs:
• Aggressor is willing to crash through barriers to reach facility
• Perimeter defining standoff must be capable of stopping the threat vehicle
For both cases, standoff distance is the best mitigation

For stationary vehicle bomb:
• Boundary is defined such that a vehicle crossing boundary draws attention and initiates response force action
• Maximize distance from parking areas

For moving vehicle bomb:
• Boundary must resist the vehicle
• Determine design speed based on roadway layout
• Minimize direct approaches
• Define passive and active barriers

3.2 Tactic: Exterior Attack

This tactic is mainly focused on small improvised explosive devices
The site design can incorporate a exclusive standoff zone to keep aggressors away from the building and limit their ability to place devices near the building or throw devices towards the building
Clear zone can also be provided around the building so that devices are easier to detect.

3.3 Tactic: Standoff Weapons

Standoff weapons include mortars, RPGs, and ballistics

Site Design Considerations:
• Minimize Vantage Points, locate facility far from vantage points
• Consider potential use of predetonation screen (for RPGs) as perimeter barrier defining standoff if that is applicable tactic
• Use of obstruction screens or landscaping to block sightlines


3.4 Tactic: Forced Entry

Tactic involves various levels of tools and explosives to attempt to breach the security of the facility.

Site Design Considerations:
• Clear zone, avoid features that provide concealment for aggressors
• Avoid siting the facility near utility passages that may aid aggressor or secure the utility access points
• Focus on security lighting to support IDS
• Provide additional fencing or barrier at facility perimeter if necessary
• Significant distance between first detection layer and building causes
delay and exposes aggressor to further detection possibilities

3.5 Tactic: Visual Surveillance, Eavesdropping

Similar to standoff weapons, you want to eliminate or control vantage points including nearby buildings
Provide clear zone adjacent to buildings so aggressors can’t hide near the building
Consider using perimeter barrier to provide concealment and obscure assets