Backscatter Machines Not Effective at Detecting Plastic Explosives

[goalieca]

I was waiting for this paper to be published. Basically, xrays are deflected more by higher "Z" materials and this contrast is what creates the pixel values in the image. This means the heavier nuclei like that in calcium in our bones (z=20) deflect them a lot better than the carbon in our soft tissues. I'm no explosives expert but I understand that these are made from the same elements in our soft tissue like H,C,N,O (z=1,6,7,8).

edit: Drugs too. Generally they are just organic molecules.

[karzeem]

It's disconcerting that this — the most thorough public study of the machines' effectiveness — is a simulation. In a sane environment, we'd be allowed to know what happens when you actually, you know, test the machines.

[physcab]

I used to develop explosives detection technology that we were hoping to sell to Smiths or TSA in a government contract. We were a research laboratory hoping to get our technology out into "industry". TSA and Smiths have their own "standards" for what they will use as basis for whether the detection methodology is viable, but they don't give those numbers or those materials out. There was a leaked document earlier this year (last year?) that contained some of this information and that was a Big Deal. I remember it took months to get something as simple as a Limit of Detection threshold that TSA benchmarks for each machine they procure.

In fact, one of the main reasons why I left is because it seemed so futile. We had very few customers to sell to, and yet we could never determine what they wanted or what channels were available to us to get it tested.

[pmichaud]

Would it be difficult to simply shape the plastic explosive around a part of your body to make it blend? I don't mean to be crass, but for example, what if you created a penis shaped sheath around your real penis? Wouldn't that just look like a larger penis to the scanner? Breasts would be easier maybe. But what about just fat rolls on the belly of a fat man?

This technology is unworkable in practice.

[Estragon]

Anyway, this is ignoring the obvious hiding place which the backscatter machine can't possibly resolve: the rectum. You could store a huge amount of plastic explosive in there in a form which would be very easy to retrieve (just shape it like a stiff shit.)

Can't wait till they plug this hole. (So to speak.)

[Bud]

The machines are, however, extremely effective at making money for Michael Chertoff. Which is their intended function.

[electromagnetic]

Honestly I'm not surprised, given the binders low density it was always going to be possible to dilute the explosive while keeping it still dangerously explosive and reduce its density down to water density (IE body).

[noamsml]

I've always wondered if airport security in general is ultimately a detriment. After all, it involves getting tons of people together at one spot. What's stopping a terrorist from blowing themselves up in the line for security?

[Nick_C]

This is one of Bruce Schneier's constant themes.