Physical security describes measures that prevent or deter someone from accessing a location or information. It can be as simple as a closed door or as complicated as a military installation.
In the security field there are three primary elements to physical security; obstacles, alarms and the security response.
Obstacles are intended to slow threats, but will not be sufficient to stop a serious threat. They are stand alone and usually unattended items such as locked doors, razor wire barriers and shatterproof windows.
Slightly more complex obstacles can include:
- Access cards and combination looks on doors
- Doors that must be pulled to enter or exit an area
- Revolving doors or turnstiles which allow one person at a time to advance
- Vehicle barriers controlled by access cards
Having a double set of locked doors is very effective. The first that opens into an enclosed area and the second that can not open until the first is closed. This is a very good obstacle for at least two reasons. Any person entering a double door area knows that exiting by the doors will be very difficult. The second of the double doors is often controlled by an employee who can make a decision to open the door or not.
These double door areas are often equipped with video surveillance and alarms.
Alarms are to both alert security response teams and to unbalance an attacker. Loud alarms, strobe lights or bright lights are common alarms.
More complex and interactive alarms include:
- Closed-circuit television cameras with motion detectors
- Roving security patrols
- Guard dogs
Although it may sound unusual, peacock and geese are used in security because their distinctive cries can act as a warning when people approach but to the common person they appear harmless, even attractive.
Security response is used to repel or catch attackers once an incident has already taken place. Security response is usually left to the police, but armed private security personnel are used when appropriate.
Security response teams train in the actual situation to become accustomed to the sights and sounds of active alarms and to remove the confusion caused by these alarm. A standard attacker will not have this training and react poorly to a changing environment.
If the security response team is properly equipped with night vision material, flood lights can be doubly effective. First to help security response teams identify exactly where the intruder is located and then, as the team approaches the area, all lights are turned off giving the intruder night blindness.
Private security response teams normally are based on site or close to the site and work closely with the local police
3 element combinations
Each of the 3 elements; obstacles, alarms and security response can be used to augment another element. For example:
- A fence originally designed to be an obstacle can become an alarm by attaching motion detectors
- Double fenced areas with guard dogs
- Placing signs that say there is an alarm makes that alarm an obstacle
- A security response team that is visible on site acts as an obstacle and as an alarm
Physical security measures intended to prevent or deter someone from accessing a location or information can never be 100% effective. A locked door will keep a common criminal from entering a centrally located building at night, but that same criminal will break into an isolated house. A determined terrorist will always be able to reach some objective, as long as he is wiling to change his target to reach whatever is easiest.