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Putting a device on its own tray means that an algorithm can apply heuristics to it to determine if it should receive a wipe test or additional human screening.

Putting a device on its own tray means that an algorithm can apply heuristics to it to determine if it should receive a wipe test or additional human screening. By placing the items onto a tray, the orientation of the device is more likely to be consistent and not obscured by other objects in the line of sight of the scanner, making algorithmic object recognition easier when a 2D scanner is used or if the bag contained items that make the data harder to process. Imagine if your goal was to get a weapon through security, what would you do? - Enclose it in a fluid or gel-filled case that appeared similar to a rechargeable battery pack on the scanner. - Enclose it in an appropriately sized shielded sub-enclosure of a common device, so that it appeared similar to the unaltered device on the scanner. For some reason laptops were identified as a likely device for this sort of use-case, hence the ban on laptops for flights originating from some places. So after the ban the adversaries likely decided to try using a boombox or a SLR camera to house a weapon, and maybe even tried an electronic drum pad or other less common device. Consider what kind of information the scanner obtains about the objects being scanned. Some is 2D but newer ones area increasingly 3D. So you have a 3D capture of the various relative densities and thicknesses of materials used to construct a device. Chances are machine learning algorithms are very good at determining which scan is an unaltered electronic device and which has been altered (additional wires, components, materials included). It's also necessary to train the system, so asking travelers to place their digicams, drum pads, etc., in a separate bin allows the scans to be used as training data for unaltered device characteristics, and help officials learn how to train the algorithms to detect subtle modification or alteration of devices. Chances are the same kind of highly advanced machine learning is being applied to the live video of passengers lining up for screening, with face, vital sign, and body carriage recognition algorithms designed to detect anxiety, deception, etc. For example, if you are rocking back and forth with a clenched chin and elevated heart rate that might be a small data point which (if combined with a laptop that has a >10% probability of having been altered) might result in a human screening and pat down. When filmed at high frame rate, heart beats are detectable via blood vessel coloration changes. Animals (like humans) are very easy to analyze this way with the right hardware and algorithms.

javajosh 9y ago
It's strange to me that we screen for weapons at all, other than explosives. The cabin is sealed. There is a marshal on the plane to limit gun/box-cutter level damage. At that point the plane itself is no more dangerous (actually considerably less dangerous) than an ordinary subway car. With explosives, I've always thought an internal smuggle would work the best. I mean, you're going to suicide anyway, so why not stick C4 up your ass? Or if you're really serious, have some surgically installed into you. One threat would be a small shaped charge to open the cabin, but that seems very unlikely. Last but not least, the WMD threat of biological weapon, 12 Monkeys style, which is a) not specific to planes and b) impossible to guard against, once the weapon is lost.
- grandalf 9y ago
  I agree. I think that the threat posed by weapons was already fully mitigated on the day of 9/11 when the passengers on the last aircraft tackled the hijackers in spite of the box cutters. All this with no marshal, no sealed cabin door, etc. The airport screening stuff has been a fiasco that is far more political and psychological than based on actual risk reduction, and the additional cost and time it takes to go through security has cost the economy billions in lost productivity. I think that the big target at present is actually explosives. I think that C4 resembles the contents of a typical LiIon cell when viewed on a scanner, or could be made to appear quite similar if prepared by someone moderately skilled who had access to (or knowledge of) the scanner and the physics behind it. Your point about a subway is interesting because we've seen no attacks on subways in the US since 9/11 and even a failed, low-budget attack would result in massive subway line closures and military presence in the subway for months, making it an effective fear-creation attack that would cost a city hundreds of millions of dollars, and potentially much more in lost productivity and mental anguish. I think the reason we haven't seen those attacks is because so few people would actually want to do them. A can of gas brought into a subway car in a backpack and ignited while the door was closed, combined with an armed shooter using a handgun would cost < $500 and would easily result in widespread closures. If two individuals did this same attack on two separate lines on the same morning, the financial damage would multiply substantially, even if nobody was killed. Suddenly there would be TSA scanners in all subway entries and it would take an extra few hours to ride a few stops. But on a plane, even a small explosive charge can take the aircraft out of the sky, so I think there is still motive for attackers to try this vector, but if the goal is to make airplanes crash it would be far more effective to use a high powered rifle near an airport and actually shoot at the aircraft. Some airports offer geographical features where this attack would be particularly effective. That we haven't seen anyone do this also suggests strongly that there is virtually nobody who wants to harm American citizens living in the US, or perhaps that all those who do have extremely grandiose ideas for attacks that are very unlikely to succeed. The 9/11 attacks were a brilliant way to weaponize aircraft, but after that was used once it becomes a lot harder to use it again. My guess is that if there ever is another large attack it will be something completely different. The first WTC bombing failed, but (similar to 9/11) relied on a very open loophole (fertilizer + van + parking garage under skyscraper). So I think authorities should be focusing on identifying the attack vectors that we are still vulnerable to that haven't been tried.

javajosh 9y ago

It's strange to me that we screen for weapons at all, other than explosives. The cabin is sealed. There is a marshal on the plane to limit gun/box-cutter level damage. At that point the plane itself is no more dangerous (actually considerably less dangerous) than an ordinary subway car. With explosives, I've always thought an internal smuggle would work the best. I mean, you're going to suicide anyway, so why not stick C4 up your ass? Or if you're really serious, have some surgically installed into you. One threat would be a small shaped charge to open the cabin, but that seems very unlikely. Last but not least, the WMD threat of biological weapon, 12 Monkeys style, which is a) not specific to planes and b) impossible to guard against, once the weapon is lost.

grandalf 9y ago
I agree. I think that the threat posed by weapons was already fully mitigated on the day of 9/11 when the passengers on the last aircraft tackled the hijackers in spite of the box cutters. All this with no marshal, no sealed cabin door, etc. The airport screening stuff has been a fiasco that is far more political and psychological than based on actual risk reduction, and the additional cost and time it takes to go through security has cost the economy billions in lost productivity. I think that the big target at present is actually explosives. I think that C4 resembles the contents of a typical LiIon cell when viewed on a scanner, or could be made to appear quite similar if prepared by someone moderately skilled who had access to (or knowledge of) the scanner and the physics behind it. Your point about a subway is interesting because we've seen no attacks on subways in the US since 9/11 and even a failed, low-budget attack would result in massive subway line closures and military presence in the subway for months, making it an effective fear-creation attack that would cost a city hundreds of millions of dollars, and potentially much more in lost productivity and mental anguish. I think the reason we haven't seen those attacks is because so few people would actually want to do them. A can of gas brought into a subway car in a backpack and ignited while the door was closed, combined with an armed shooter using a handgun would cost < $500 and would easily result in widespread closures. If two individuals did this same attack on two separate lines on the same morning, the financial damage would multiply substantially, even if nobody was killed. Suddenly there would be TSA scanners in all subway entries and it would take an extra few hours to ride a few stops. But on a plane, even a small explosive charge can take the aircraft out of the sky, so I think there is still motive for attackers to try this vector, but if the goal is to make airplanes crash it would be far more effective to use a high powered rifle near an airport and actually shoot at the aircraft. Some airports offer geographical features where this attack would be particularly effective. That we haven't seen anyone do this also suggests strongly that there is virtually nobody who wants to harm American citizens living in the US, or perhaps that all those who do have extremely grandiose ideas for attacks that are very unlikely to succeed. The 9/11 attacks were a brilliant way to weaponize aircraft, but after that was used once it becomes a lot harder to use it again. My guess is that if there ever is another large attack it will be something completely different. The first WTC bombing failed, but (similar to 9/11) relied on a very open loophole (fertilizer + van + parking garage under skyscraper). So I think authorities should be focusing on identifying the attack vectors that we are still vulnerable to that haven't been tried.