73. SECURITY RISKS IN ACCESS DOORS

The most common security risk/breach of an access control system is through "tailgating" or "piggybacking (security)" which refers to the practice of an unauthorized person following an authorized person through an opened door. Tailgating implies that the person who received authorization is not aware that another person has followed them through the door, while piggybacking implies that the credentialed person has agreed to let another person through the open door. There is a risk that an intruder could open a door by accessing exit button wiring.


In most cases exit button provides a normally open input. If the intruder shorted the exit button input, the electric lock would unlock because the system would think that the exit button was pushed, and no alarm would be generated because most access control systems discard exit button events as unimportant.
The intruder could also open a door by shorting the door contact wires and cutting the wires going to the electric lock or, depending on the type of the lock, providing power to it from a portable source. The door contact input provides a normally closed contact, therefore if the wires were shorted no door open alarm would be generated. These two intrusion options are possible in both door wiring configurations:


In "Home run" configuration one control panel is used to control multiple doors. As the distance between the control panel and the doors increases, an intruder has more chances to find access to the wires. The threats may be reduced by employing resistor supervision, digitally supervised inputs and external digitally controlled relays. Distributed configuration with intelligent readers may be even easier to compromise if special protection measures are not taken: by removing the reader from the wall an intruder can gain access to all the wiring.


Of course tamper alarm most likely would be triggered, but that would not prevent the intruder from opening the door. One option to eliminate this risk is NOT to use intelligent readers in high-risk areas like outside doors or gates. The second option is to install a special input/output module for controlling door hardware. Instead of being controlled directly by the reader, door contact, exit button and electric lock are connected to the input/output module, which is located on the secure side of the door.