Source: Wired

After an alleged terrorist unsuccessfully tried to detonate his explosive underwear on a Christmas Day flight to Detroit, current and former American officials are now using the failed attack to push for more airport scanners to spot such explosives — and a lot more.

The Transportation Security Administration in recent years has tried out a series of “whole-body imagers” to look for threats that typical metal detectors can’t find. These systems are the only way that smuggled explosives, like the one officials say was brought on the Christmas flight, can be reliably found.

“You’ve got to find some way of detecting things in parts of the body that aren’t easy to get at,” former Homeland Security chief Michael Chertoff told The Washington Post. “It’s either pat-downs or imaging.”

The problem, privacy advocates say, is that a zap from one of the devices amounts to a “digital strip search” from a system “designed to capture, record, and store detailed images of individuals undressed.”

TSA has worked with two basic technologies to upgrade its passenger screening systems. Millimeter-wave sensors emit radio frequencies, and measure the differences in radiated energy. The result is a detailed, 3-D image of the passenger that looks sort of like a photo negative.

The TSA currently has 40 of these machines installed at 19 airports. Six airports have a machine each for primary screening. The other 34 are used for follow-up searches at 13 airports. The agency handed out a $25 million contract to Rapiscan Security Systems in October for 30 more of the machines.

Similarly, backscatter x-ray scanners send out low-intensity beams, and watch how the x-ray photons get reflected back. (Old-school machines simply sent the x-ray through the object.) “Elements with lower atomic numbers (fewer protons) on the periodic table scatter X-ray photons very powerfully, while elements located farther down on the periodic table tend to absorb more photons than they scatter.

Most organics are located closer to the start of the periodic table. So backscatter systems are very good at imaging organic material — much better than dual-energy systems.

They easily pick up the scatter patterns of drugs and explosives and body parts,” notes one helpful description. TSA has ordered 150 backscatter units, after 46 of the sensors were used at 23 airports in a pilot project.

But it’s unclear how far the TSA will be allowed to go in deploying these systems. Because the same technology that allows the scanners to find explosive underwear can also provide some rather revealing glimpses of passengers’ bodies.

The agency says there’s no privacy problem. “Facial features” (and, presumably, other body parts) “are blurred when our officers see the images,” the TSA insists. Nor will the agency “keep, store or transmit images. Once deleted, they are gone forever…. For additional privacy, the officer viewing the image is in a separate room and will never see the passenger, and the officer attending to the passenger will never see the image.”

“These images are friendly enough to post in a preschool. Heck, it could even make the cover of Reader’s Digest and not offend anybody,” the TSA noted on its blog.

But privacy groups aren’t exactly comforted by the agency’s assurances. TSA has already reversed earlier stands on the scanners, the groups say.

The Electronic Privacy Information Center filed a lawsuit against the Department of Homeland Security on Nov. 9, to force it to give up information about the scanners. “TSA has stated that whole-body imaging would not be mandatory for passengers,” the Center noted in its complaint. “On Feb.18, 2009, TSA announced that it would require passengers at six airports to submit to whole-body imaging in place of the standard metal detector search, which contravenes its earlier statement.”

The House of Representatives voted 310 to 118 in June to pass a measure that prohibits the TSA from using whole-body imaging as a primary means for screening passengers. The legislation’s prime sponsor, Rep. Jason Chaffetz, said Sunday that he stands by the measure. “I believe there’s technology out there that can identify bomb-type materials without necessarily, overly invading our privacy,” he told the Salt Lake Tribune.

“Yes, there is some brief violation of privacy with a full-body scan,” Rep. Peter King, the top Republican on the House Homeland Security Committee, told Face the Nation. “But on the other hand, if we can save thousands of lives, to me, we have to make that decision, and we have to come down on the side of saving thousands of lives.”

But that logic makes about as much sense as the TSA’s new rules forcing passengers to stay in their seats for the last hour of a flight, says security guru Bruce Schneier. “It’s the same magical thinking we’re used to getting from the TSA,” he tells Danger Room. “Descend on what the terrorists happened to do last time, and we’ll all be safe. As if they won’t think of something else.”