Perimeter Security refers to natural barriers or built fortifications to either keep intruders out or to keep captives contained within the area the boundary surrounds.
Since at least the Roman Empire, fortifications, walls and barriers have been an important part of protecting sovereign territories and private property. Perimeter security is designed with the primary purpose to either keep intruders out or captives contained within the area the boundary surrounds. Both natural and manmade barriers can serve as perimeter security.
Governments use perimeter security not only for the safety of their citizens, but to control the flow of commerce and immigration, as well as to protect vital infrastructure from vandals and terrorists. Property owners and organizations of all sizes use various man-made technology to achieve varying degrees of perimeter security.