5 ms·

Backscatter Machines Not Effective at Detecting Plastic Explosives

78 points by pmichaud 16y ago

electromagnetic 16y ago
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).
goalieca 16y ago
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.
pmichaud 16y ago
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 16y ago
  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.)
  - gojomo 16y ago
    Thankfully, Al-Qaeda has no familiarity with heroin smuggling 'mules'. Wait, what's that you say? They've got base camps in the world's major heroin-producing region and make money from heroin? Hmm.
    - mahmud 16y ago
      Heroine is not smuggled out of Afghanistan through rectums, no, it goes out in caravan trucks with security detail.
      - deleted 16y ago
        [deleted]
  - tptacek 16y ago
    Christopher Hitchens wrote an article for Slate a week ago pointing out that a recent (successful) assassination in Saudi was carried out with a body cavity PETN bomb.
    - slug 16y ago
      If it's I think it is, it was an unsuccessful attempt of assassination of a Saudi prince, with a high rank in the anti-terrorism agency, although he barely escaped. Supposedly the assailant was thoroughly searched and finding nothing suspicious , the security people let him approach the prince. The bomb was detonated by remote control, through a message or call to his cellphone.
      - scdlbx 16y ago
        The assailant's body did a pretty good job of containing the explosion. The assailant didn't make it, but everyone else relatively okay. http://www.cbsnews.com/stories/2009/09/28/eveningnews/main5347847.shtml http://www.cbsnews.com/stories/2009/09/28/eveningnews/main53...
  - lkoujhghjk 16y ago
karzeem 16y ago
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 16y ago
  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.
  - jonhohle 16y ago
    You (they) should have asked a few congress-critters to be on your board of directors. You still might not get a copy of the standards, but you'd likely have been selling machines.
  - rdtsc 16y ago
    That happens quite often with government contracts. There is a lot of back-room deals, knock-knock, wink-wink, "I'm a friend of a friend" kind of stuff. There is some superficial formality and fake fairness tot the bidding process but it ultimately comes to who you know. Requirements are kept vague and only the "friends" are notified of what they are. Later during the review surprise! one company just happens to exactly read the mind of the buyers and gets picked. This is even worse in the security related areas as the vagueness of requirements is justified to be security related. Your best bet would have been to hire an ex-General or an ex-TSA high ranking official. Or at least hire someone who was a college roommate of some TSA official.
Bud 16y ago
The machines are, however, extremely effective at making money for Michael Chertoff. Which is their intended function.
noamsml 16y ago
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 16y ago
  This is one of Bruce Schneier's constant themes.

78 points by pmichaud 16y ago

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).

goalieca 16y ago

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.

pmichaud 16y ago

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 16y ago
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.)
- gojomo 16y ago
  Thankfully, Al-Qaeda has no familiarity with heroin smuggling 'mules'. Wait, what's that you say? They've got base camps in the world's major heroin-producing region and make money from heroin? Hmm.
  - mahmud 16y ago
    Heroine is not smuggled out of Afghanistan through rectums, no, it goes out in caravan trucks with security detail.
    - deleted 16y ago
      [deleted]
- tptacek 16y ago
  Christopher Hitchens wrote an article for Slate a week ago pointing out that a recent (successful) assassination in Saudi was carried out with a body cavity PETN bomb.
  - slug 16y ago
    If it's I think it is, it was an unsuccessful attempt of assassination of a Saudi prince, with a high rank in the anti-terrorism agency, although he barely escaped. Supposedly the assailant was thoroughly searched and finding nothing suspicious , the security people let him approach the prince. The bomb was detonated by remote control, through a message or call to his cellphone.
    - scdlbx 16y ago
      The assailant's body did a pretty good job of containing the explosion. The assailant didn't make it, but everyone else relatively okay. http://www.cbsnews.com/stories/2009/09/28/eveningnews/main5347847.shtml http://www.cbsnews.com/stories/2009/09/28/eveningnews/main53...
- lkoujhghjk 16y ago

karzeem 16y ago

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 16y ago
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.
- jonhohle 16y ago
  You (they) should have asked a few congress-critters to be on your board of directors. You still might not get a copy of the standards, but you'd likely have been selling machines.
- rdtsc 16y ago
  That happens quite often with government contracts. There is a lot of back-room deals, knock-knock, wink-wink, "I'm a friend of a friend" kind of stuff. There is some superficial formality and fake fairness tot the bidding process but it ultimately comes to who you know. Requirements are kept vague and only the "friends" are notified of what they are. Later during the review surprise! one company just happens to exactly read the mind of the buyers and gets picked. This is even worse in the security related areas as the vagueness of requirements is justified to be security related. Your best bet would have been to hire an ex-General or an ex-TSA high ranking official. Or at least hire someone who was a college roommate of some TSA official.

Bud 16y ago

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

noamsml 16y ago

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 16y ago
This is one of Bruce Schneier's constant themes.