As penetration testers, we spend most of our time working with different types of networks, applications, and hardware devices. Physical security is another fun area we get to work in during physical social engineering penetration tests and red team engagements, which sometimes includes attempts to gain entry into facilities or sensitive areas within them.

Just like when we’re testing a virtual network’s defenses against intruders, pentesters need to put themselves in the mindset of attackers when testing physical security — and that means thinking creatively.

One classic method of gaining physical access is “tailgating,” where you wait for someone else to be going into or coming out of where you want to go, so you can follow them in before a door closes. To help pentesters simulate an attacker who can tailgate without suspiciously hovering around the door, we’ve come up with a neat little device to help with outward-opening doors with ferromagnetic metal frames, like steel entry doors. This tool is one more way pentesters can recreate the thought process of attackers — and help organizations outsmart them.

But first, of course, we want to caution that this is something that should only be used for legitimate purposes, when you have authorization or authority to do so. While we encourage other testers to try this out themselves and use it for customer engagements, this device is patent pending, and we request that you not manufacture, sell, or monetize it.

It’s it! What is it?

We start by placing our little door holder on the door frame, on the side of the door that opens:

When someone opens the door, it will push the long leaf of the hinge forward:

As the door opens further than the long leaf of the hinge, it falls back down behind the door:

And while the person who was exiting the door is hopefully on their merry way and not looking back to see if the door will close behind them, our little device will make sure it doesn’t:

More than one way to peel an orange

We’ve made a few versions of this using lock hasps. Another common hinge with a longer side would be your standard t-hinge. This one was made with a few bar-style neodymium magnets:

We’ve also made a miniature version using cup-style neodymium magnets:

Important tips

Neodymium magnets can slide around a good bit on smooth surfaces. Putting some grippy tape on the back of the magnet can help keep it from sliding around or scratching paint. Electrical tape and gorilla tape have worked well.

Likewise, having some padding on the leaf that contacts the door is important to prevent it from scratching paint.

Countermeasures

This tool makes it easier to enter a building or secure area by tailgating. By simulating an attacker with a high level of skill and ingenuity, the tool can help reveal weaknesses in organizations’ physical security protocols — and what countermeasures might be more effective.

If you have an electronic access control system, consider configuring it to trigger alerts if a door has been left open for too long. But the best place to start is to make sure your physical security policies and security awareness training educates staff about tailgating, encourages them not to let someone follow them in, and emphasizes making sure that doors close behind them.

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