From the mind of Gabriel Shear
Saturday October 24, 2015
How To Bypass Sliding Gate Security
This information is provided for educational purposes only. The author nor the website are responsible for misuse of information provided below.
I’m going to outline a pretty simple and effective method for bypassing the security code/card locks on about 90% of all sliding security gates.
This method relies on understanding how sliding gates works and how to use this knowledge to your benefit, if ever the need may arise.
A sliding gate typically consists of a few different parts:
- Gate drive
- Motor controller
- Limit sensors
- Safety sensors
- vehicle sensors
- Entry keypad or proximity card reader
Most gates you will see are typically chain driven and use a large roller chain and sprocket to transmit the motors rotational force into a linear one to move the gate back and forth. The other style is the direct drive. Usually only seen on high security gates, it consists of a large flat bar attached to the gate which itself is pinched between two rubber drive rollers that spin and move the bar forwards and back, opening and closing the gate.
Here are the styles:
Low Security Chain Drive Gate
High Security Direct Drive Gate
Beyond the gate and motor itself, the system needs a way to control:
- When the gate should open and close
- How far it needs to open and close
- When to stop (so as not to crush anyone or thing)
To achieve the above needs, a motor controller is used with an array of sensors that help it to determine when to turn on the motor and in what direction.
Typical sensors include:
Limit switches – They tell the controller when the gate has reached its fully open or closed position.
Safety sensors – Such as crush strips on the edge of the gate, so that if it hits a car or person it can stop the motor to prevent injury or damage.
Vehicle sensors – Inductive loops placed in the ground can tell the system when a vehicle is on either side of the gate or even in the gates path.
Access control – Entrance keypads or proximity card readers. Either integrated in to the controller or part of a larger building system. They allow authorized opening of the gate.
All these sensors work in conjunction with the motor controller to determine the state of the system and along with some programming what it should do an any give scenario. It is the vehicle sensors that we are going to be attacking in order to open the gate.
While a user is required to provide some sort of security credential to the system in order to operate the gate. On about 90 percent of gates a vehicle that is leaving is usually sensed by a vehicle detection loop and the gate is automatically opened so the vehicle may leave.
This vehicle detection loop consists of a loop of wire embedded in the ground in the path of vehicle. I works through the principle of electromagnetic induction. An explanation of how this works is that an alternating electrical current is passed through the loop. At a given frequency the loop will have a specific inductance. This inductance resists the flow of electrical current and is compared against a known value in the controller. When a metal object such as a vehicle drives over the loop. The metal acts like the metal core of a transformer and increases eddy currents do to the inductance of the loop. The increases in eddy currents are then seen by the controller and used to tell the system to open the gate.
The thing is that anything that increases the inductance of the loop will fool the system into believing a vehicle is there. any metal will increase the inductance and fool the system.
The way to bypass the security of the gate would be to slide or throw a large piece of metal over the loop. They are easy to spot as they are usually visible as cuts in the concrete/black top (as shown above). The corners of the loop are more sensitive than the center or edges. Most gates have a rather large gap underneath to slide something like a tire iron or piece of sheet metal or a length of chain. Hell one could even break the pedestal holding the keypad and use that if one was desperate enough. In either case, if the metal piece is large enough it will trigger the gate to open and the gate security has just been bypassed.
Not all gates open using vehicle detection loops, but most do and like I’ve said this should work on about 90% of gates you might encounter. I hope this information is informative and enlightening.