Perimeter Security, Part I

The first line of defense for any organization is it's perimeter control. As mentioned before, physical security should be applied in a layered approach. If a criminal is able to circumvent outer controls such as fences and locks, there must be more controls inside to delay the attacker until a response can be made.

Fences

Fences can serve as an effective outer physical barrier. They are likely to only delay the most determined attackers, but they give a strong psychological impression that a company is serious about security. When installing fencing, many companies choose to also place shrubs or bushes in front to improve aesthetics. Vegetation can greatly improve the look of the fence, but also may damage the fence over time, so proper maintenance is key.

When choosing a fence there are multiple factors to consider. Height, gauge, and mesh size are very important qualities of fencing. Fences in the three to four foot height range will stop only the most casual attackers as these can be easily jumped. Six to seven foot fences are considered too high to easily climb, and eight foot or higher fences are used when you're really serious about security. Often with these higher fences, barbed or razor wire will be strung along the top to really convince people that trying to climb it would be a bad idea.

The gauge of the fence refers to the thickness of the wire that makes up the body. The higher the gauge number, the thinner the wire. Below is a table summarizing the most common sizes:

• 11 gauge = 0.0907-inch diameter
• 9 gauge = 0.1144-inch diameter
• 6 gauge = 0.162-inch diameter

The mesh size of the fence refers to how much distance is between the wires. A smaller mesh size makes it more difficult to climb or cut. Common mesh sizes are 2 inches, 1 inch, and 3/8 inch.

One last consideration when installing fences is that the posts and wire frame must be installed deep enough into the ground to prevent anyone from trying to dig underneath it.