Physical Security - Overview

Overview

Physical security is primarily concerned with restricting physical access by unauthorized people (commonly interpreted as intruders) to controlled facilities, although there are other considerations and situations in which physical security measures are valuable (for example, limiting access within a facility and/or to specific assets, and environmental controls to reduce physical incidents such as fires and floods).

Security inevitably incurs costs and, in reality, it can never be perfect or complete - in other words, security can reduce but cannot entirely eliminate risks. Given that controls are imperfect, strong physical security applies the principle of defense in depth using appropriate combinations of overlapping and complementary controls. For instance, physical access controls for protected facilities are generally intended to:

• deter potential intruders (e.g. warning signs and perimeter markings);
• distinguish authorized from unauthorized people (e.g. using pass cards/badges and keys)
• delay, frustrate and ideally prevent intrusion attempts (e.g. strong walls, door locks and safes);
• detect intrusions and monitor/record intruders (e.g. intruder alarms and CCTV systems); and
• trigger appropriate incident responses (e.g. by security guards and police).

It is up to security designers, architects and analysts to balance security controls against risks, taking into account the costs of specifying, developing, testing, implementing, using, managing, monitoring and maintaining the controls, along with broader issues such as aesthetics, human rights, health and safety, and societal norms or conventions. Physical access security measures that are appropriate for a high security prison or a military site may be inappropriate in, say, an airport, an office, a home or a vehicle, although the principles are similar.

Physical security is not uniquely human. The practice of actively defending a territory against intruders or opponents is very common in the animal kingdom. Physical security is also not a modern phenomenon. The technology is continually evolving along with the threats. Physical security controls that were considered adequate in the past tend to be insecure today due to advances in the knowledge and capabilities of attackers. In the same way, controls that currently appear strong are likely to prove vulnerable in future, in ways that may not be obvious right now.