Intrusion Detection
Physical security describes security measures that are designed to deny unauthorized access to facilities, equipment and resources, and to protect personnel and property from damage or harm.
Since the dawn of civilization, maintaining perimeter security has been a top priority. Having some form of it-whether a city wall, a moat or even trained animals-has always been critical for stopping, delaying or deterring a perimeter breach.
Fundamentally, good physical security is a combination of four defensive principles: deterrence, delay, detection and denying a breach. The first two actions are considered passive defense while the latter two are active in nature.