Vulnerability of Sensors

All sensors, whether interior or exterior, are vulnerable to attack. Some precautions will help reduce their vulnerability:

• Tamper-protection methods generate a “tamper” alarm if an attacker attempts to defeat the sensor. Because signal-processing circuitry for exterior sensors is generally more vulnerable to tampering and defeat than the circuitry for interior sensors, enclosures must be located and installed properly. Adequate physical protection must be provided.
  
  
• Signal-line supervision involves imposing a unique noninterfering signal on the line between the sensor and the processor. If some condition of that signal changes (as would happen if an attacker tried to bypass the sensor), the alarm-monitoring system shows a tamper alarm condition. This is useful in detecting natural degradation of the signal or other maintenance problems, not just attacks.
  
  
• A self-test capability can assure that the sensor is operating correctly and performing its function.
  
  
• Proper installation makes exterior sensors less vulnerable to defeat. Sensors must be mounted inside the secure area where they are less vulnerable to attack. Follow the manufacturer’s instructions and install the sensor as instructed in the proper environment.
  
  
• Some sensors, notably interior passive infrared sensors and other motion sensors, have external lights or light-emitting diodes that light up when the sensor detects something. Often, these lights are used when the sensor is being tested. These lights and any other visual or audible indicators should be covered or disabled when they are not being used for testing. An attacker or someone gathering intelligence does not need to know whether your sensors are operating. In the case of passive infrared sensors, an attacker could discern the sensor’s pattern coverage area by discretely walking in the public reception area and observing the light or light-emitting diode.
  
  
• Most commercial alarm system installers use surface-mount sensors. They are less expensive and easier to install than flush-mounted or concealed sensors. Visible surface-mount and flush-mounted sensors should not be the only sensors installed. If possible, conceal some sensors so an attacker or someone gathering intelligence cannot see them. Consider installing some “dummy” sensors—empty sensor shells that contain no electronics but appear to be connected to the alarm system. The objective is to keep the attacker from assessing your intrusion detection system accurately. Federal rules do not prohibit deceiving those who would harm your facility and its occupants.