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I have a storage space full of information assets. The room itself is sound; there are no windows, the walls go all the ceiling, and there is only a single entrance with two good stout doors and high precision locks. At the risk of sounding purposefully cagey, assume a 7+-pin master key system with anti-pick features.

My biggest concern is the mullion, the bolted in steel vertical as illustrated in this picture, separating the doors. I feel that it is better than he doors latching to each other, however it also seems like a weakness. Does the mullion present an undue risk? If so, is there a commonly accepted mitigation path?

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Can you give better description of locks? – StupidOne Aug 15 '12 at 15:11
@StupidOne: I at least added something on the locks, it is purposefully vague but hopefully not uselessly so. – Scott Pack Aug 15 '12 at 15:38
If your doors are like those in the photo I would be more concerned with someone shimming the latch or fishing around the frame for the panic bars. – Bill Aug 15 '12 at 16:15
I would be most concerned about someone drilling through the apparently hollow mullion just to do reconnaissance on the assets inside. Sometimes knowing what is inside is all an adversary needs. – this.josh Aug 13 '13 at 3:13
@this.josh: How is that a different risk than drilling through the door, door frame, or wall? – Scott Pack Aug 13 '13 at 11:36

It depends on the construction of the mullion. Some are bolted on, some frames come as a solid piece including the mullion, and some mullions are a cosmetic fascia. If it is bolted on as long as the bolts are good quality and bolt into a metal frame then it's as good as a one-piece metal frame for most purposes, it's when it's a cosmetic piece that you have a problem.

Some mullions are simply a piece of 2x4 covered in drywall and plaster. These won't keep out anyone with a crowbar for very long.

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I'd ask why the need for a mullion in a double door way when you could just have a single large doorway instead? It would be preferable to have one single high-strength and high-security door as part of a solid frame/wall rather than two potentially weaker doors and a corresponding weak point. Certainly the mullion can be bolted in and made of solid steel. But it seems to be simply an additional point of failure for no good reason.

If you're concerned about brute force attacks, consider as well, how much effort would be needed to move it. If you put a doorway such as this at street level, it would be possible to attack it in a fashion similar to a 'ram-raid' with cars/machinery etc. If placed under/above ground then it reduces the possibility for such attacks obviously.

Hopefully that helps somewhat!

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If the mullion is (as your description suggests) a decent hunk of steel, then attacks that involve breaking it aren't really a problem. If the frame is solid (some kind of steel framing is preferable) and the mullion is secured with bolts that are:

  • a reasonable length (the majority of which should be in the doorframe)
  • a proper thickness
  • properly secured
  • sufficiently numerous
  • not all accessible from outside the room

then attacks that involve removing it are unlikely to be a problem either.

Against that sort of setup, your main problems are probably:

  • brute force against the locks and/or the point where they secure into the mullion
  • brute force against the hinges
  • lockpicking (depends on the lock, but you'd be surprised what people can pick)
  • hooking the internal mechanism - if you've got fire-escape-type crash bars like in that picture, then depending on how snugly the door fits it may be possible to hook them from outside. Of course, doing so may well trigger fire alarms, which may or may not mitigate the threat somewhat.
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