The establishment of a secure perimeter is possibly the most foundational concept in the security industry. Whether the task is to apply Crime Prevention Through Environmental Design (CPTED) principles to a new campus environment or to protect Class A national assets, the secure perimeter identifies that point at which the security program is initiated.
The technological tools that are applied at the perimeter can vary according to a number of factors, such as the specific purpose of the perimeter, the characteristics of the site and the nature of the asset.
Three Categories of Perimeter Security
It may be helpful to think about perimeter types in three categories. First, security perimeters define a line of demarcation from a public to a non-public area. Once the perimeter is crossed, new rules are in force as promulgated by the property owner or the authority having jurisdiction. In some instances, this is the only defined perimeter for a facility — college campuses generally fall into this category. As an individual turns off the public street and onto the campus, signage is normally used to inform the individual that they are now on university property, to obey posted speed limits, etc. In CPTED terms, the university is establishing territoriality. Everything else on campus is largely open to the visitor.
A second type of perimeter also establishes a line of demarcation but with an ability to detect those that violate that line. Reliable perimeter intrusion detection has been and is an essential component of security systems for the protection of assets. These perimeters provide for authorized passage through access control portals for both personnel and vehicles; however, an unauthorized penetration initiates an alarm, which signals the malevolent intent of the intruder and simultaneously initiates response activities. Depending on the facility, the response could range from notification of the local law enforcement agency to activation of an armed response team.
A third type of perimeter is defined and designed to physically deny unauthorized access. Almost exclusively focused on vehicle-borne threats, this approach arose out of the vehicle bomb attacks on U.S. Department of State (DOS) and Department of Defense (DoD) facilities beginning in the mid-1980s. The importance of this type of protection has been reemphasized with events such as the Khobar Towers bombing in the mid-1990s and, of course, recent events in Iraq. These perimeters are typically characterized by systems that can absorb the kinetic energy of a fully loaded truck traveling at high speeds; and intrusion detection systems are typically not deployed (or needed) in these circumstances.
It logically follows that different technological solutions are employed to achieve the different goals implied by the second and third perimeter types discussed above.