Sunday, December 12, 2010

Naked Body Scanner Defeated by Pancake-Shaped Explosives

These scanners are not effective, and past post have made that point. What makes this different is the type of flaw. The basic problem with the scanning system is that humans are not uniformly shaped. Bodies have certain characteristics, and irregular characteristics are what the screeners are looking for. That means a brick shaped explosive. Thin explosives on the other hand that conformed tightly to the body would be mistaken for the subject; that is, not recognized as their being anything foreign there. The message here to the terrorists is that the larger the explosive they use, the less likely it would be detected. Think about that for a second, our anti-terrorism efforts are actually encouraging the bad guys to use bigger bombs... (via)

"It is very likely that a large (15-20 cm in diameter), irregularly-shaped, cm-thick pancake with beveled edges, taped to the abdomen, would be invisible to this technology, ironically, because of its large volume, since it is easily confused with normal anatomy. Thus, a third of a kilo of PETN, easily picked up in a competent pat down, would be missed by backscatter "high technology". Forty grams of PETN, a purportedly dangerous amount, would fit in a 1.25 mm-thick pancake of the dimensions simulated here and be virtually invisible. Packed in a compact mode, say, a 1 cm×4 cm×5 cm brick, it would be detected.

The images are very sensitive to the presence of large pieces of high Z material, e. g., iron, but unless the spatial resolution is good, thin wires will be missed because of partial volume effects. It is also easy to see that an object such as a wire or a box- cutter blade, taped to the side of the body, or even a small gun in the same location, will be invisible. While there are technical means to mildly increase the conspicuity of a thick object in air, they are ineffective for thin objects such as blades when they are aligned close to the beam direction.

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