Hey there Mos and Boo fans. I'm Mos and in this video I’m
going to show you how to bypass a wire cable seal using a needle.
I’m also going to pull one apart so you can see how they work and why this bypass is so effective.
Let’s get started!
In our last tamper evident bypass video I showed you how to bypass
a fixed length seal. I also briefly showed you a green wire cable seal. I thought some
of you might be curious about how to bypass this type of seal so we decided to make this video.
A cable seal isn’t fixed length like the last seal we bypassed.
You put one end of the cable through the body of the seal and then pull it tight,
just like a zip tie.
Once the cable goes into the body, you cant pull it back out.
It only goes one way. I’ll explain why in a bit.
Here I have three different types and sizes of cable seal.
The main difference is they have different
thickness cable so they have different breaking strengths.
The cable is usually made of braided aircraft cable. This
makes it very strong and if you cut it, it will splay out making it pretty
much impossible to rejoin without looking like its been tampered with.
So if you were thinking of cutting it and feeding it back into the body,
it’s probably not going to work.
We know for a fact that this cable splays out when cut.
Back at BSides Canberra 2018, a couple of people cable sealed their own wrists
before finding out if they could bypass the seals. No one could. No one had cutters.
All anyone had were metal files so they spent two days filing themselves out.
Don’t believe me? Here you go!
And now there are warnings signs at all the security conferences since.
If you look at the cable seal body, they are usually aluminium and have serial numbers on them.
This is so you cant just cut the seal and replace it with the same type.
In the body there is a hole where one end of the cable is attached permanently.
You will also notice there is another piece of metal inserted in the middle of the body.
This is the locking mechanism for the cable.
You will see there is a second hole that runs along the edge of this metal insert.
This is where the cable gets fed into the body when you want to lock the seal.
This piece of metal is permanently attached using different methods.
One attack would be to pull this piece of metal out, which would let you remove the cable.
This is possible on some cable seals but not all.
If you look at these two, you can see the body has been squashed onto the cable,
so you would have to destroy the body to release the cable.
On this third one, you can see that there is a single
hole that is filled with some sort of metal.
It actually looks like solder in this hole.
I only have one of these and wanted to show it to you first so after I film this bit of the video
im going to go get a blowtorch out and see if I can melt this bit of metal and remove the plug.
Ok.. that didn’t work. But that’s the best part about tamper evident bypassing and lock picking.
Coming up with theories then experimenting and breaking stuff!
Seeing that didn’t work I drilled it out instead
so we could remove the centre piece and show you the locking mechanism.
This is pretty cool. Looking at the centre piece you can see this little
barbed wheel next to a piece of spring steel.
When you push the wire in, it pushes the wheel down the hill and against this spring.
The spring compresses letting the wheel go down further and the wire to slip past.
When you try and remove the wire by pulling backwards, the barbs grip the wheel pulling
it up the hill jamming the wheel and the wire against the roof of the seal body.
Thats why you cant pull the wire out.
It’s a really clever design. Nice work little wheel dude! But im tricksier than you.
To bypass the seal we need to make sure the wheel cant roll back uphill.
Luckily the little wheel has a small channel to let the cable slide over it.
And guess what fits perfectly into this channel?
This needle.. which Im definitely not storing in my pants. Ouch!
To bypass the seal, we can slide a needle along this channel and force
the wheel back down into the spring and make a smooth bridge for the wire to slide over.
Let’s show you this technique in action
All you have to do is slide the needle in under the cable.
It needs to be from the side you slid the cable in so the cable slides out along the needle.
When you put the needle in you can feel the wheel and the little channel.
It can take a few goes as the needle often slides out to the side as you pull the cable
out but after a few goes the cable is fully out and you’ve bypass the seal.
You can now open whatever it was sealing and then put it back and no one will know.
Just a note. This attack won’t work on all cable seals.
It works well on these small ones cause of the
size of the wheel and the gap between the body and cable.
We will be ordering a bunch of test seals soon so
will make another video on how to bypass those ones.
If you want to learn more ways to bypass tamper evident seals and other physical
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Until then, we will be back soon with another tamper evident bypass!