The privately funded effort to build a small stretch of border wall on private land has apparently erected slat (bollard) walls with solid panel tops. I’d just like to illustrate how absurdly easy it is for people to get past a wall with this design, even a very tall one.
Some Internet naysayers have argued that people will cut their way through it, or bring giant ladders, or dig under it. No, no, and no: that requires too much equipment, time and effort. You can get past a slat+panel wall in 15 minutes with a backpack worth of gear, barely any work, and no tools, power or otherwise.
The reason is bad design, and I think the instructions below illustrate the issue better than any standalone explanation. So let’s begin:
Step 0: You are on one side of a wall. Your backpack contains a rope ladder.
You also have:
- A length of fishing line, and an equal length of cord (paracord from the hardware store, or clothesline cord)
- A short length of of light chain, just enough to encircle a single bollard or slat
- A slingshot and a few carabiners.
Step 1: tie a small counterweight to your fishing line, and use the slingshot to fire it over the wall. Reach through and grab the counterweight from the other side.
This will allow you to hoist something up and over the wall. That’s the first design flaw of a bollard wall with a solid top: that combination lets you use the wall as a makeshift pulley.
Step two: use the fishing line to pulley up the stronger cord, suitable for hoisting up the rope ladder.
Now hoist up the rope ladder. At the point where the rope ladder reaches the bottom of the panel, use a carabiner to attach your chain to the rung that is currently at the ground.
Step three: continue pulling the ladder over until you can reach the chain from the other side. The base of your ladder may fly out of reach, so attach your cord to it.
When you can reach the chain, encircle a bollard and attach the other end to the same carabiner you used before.
Step Four: pull the ladder back to you until the chain cinches at the top panel.
This is the second design flaw of the wall: it gives you a big dang hook to hang things.
Step Five: climb the ladder, and when you reach the chain, use another carabiner to attach a rung of the front ladder; this way it is cinched on both sides, and you can climb down the other side.
Notes:
- A slight variation of these instructions will let you disassemble the ladder from the other side, if you want to carry away the evidence or use it to surmount another barrier elsewhere.
- This basic idea applies to any number of walls with slats on the bottom and some crosspiece at the top. As long as it produces a cinch point, you will have this vulnerability.
Discussion
In security engineering, we have something called a “threat tree,” or attack tree. This shows multiple paths an adversary can take in order to defeat a security system.
Sometimes we get so focused on a single line of attack (cutting through a wall) that we completely miss an attack that is much cheaper and easier. This can cause us to invest or overinvest in a technology that is extremely hackable by other means, and hence unwise.
The point of a threat tree is to provide a global perspective on what adversaries can do, and thus to provide a global perspective on how limited a security system really is, or how hard a security problem really is. That’s important if the security system is going to cost billions of dollars, or if your public policy rests upon solving the security problem.
An example I use in class (I teach security courses at a university) is bypassing locks on handle doors. Many doors in public buildings use handle openers because they are ADA compliant. An example is shown to the right. If this door is locked, you can pick the lock which requires time and expertise, and someone can build a better lock to make your job harder. Or, you can use a 6-foot length of gauge 6 copper wire from the hardware store, to reach under the door gap and pull down the handle from the other side. I and my colleagues are absentminded enough to lock ourselves out of our offices and labs, so I use this trick several times a year. Tow truck drivers use a similar trick when I lock myself out of my car.
What does that mean? It doesn’t mean doors are pointless or locks are pointless, but it does mean:
- You shouldn’t spend a bazillion dollars on the world’s best locks;
- You shouldn’t create a dire need for that door to be absolutely secure.
The threat tree tells us that a lock can only do so much, because of this alternate avenue of attack. That’s on top of other attacks, like social engineering of the custodial staff. This perspective is supposed to tell us that the security system has realistic limits, and we should neither overspend or over-rely on it.
The same lesson, I believe, applies to “The Wall.”