German Police Admit That Full Body Naked Airport Scanners Suck; 35% False Alarm Rate

from the that's-worse-than-useless dept

We’ve noted all sorts of privacy and health problems related to full body “naked” scanners — but there’s a separate but important question: do they actually work? There’s been some evidence presented that they wouldn’t have spotted a variety of recent terrorism attempts, but now German police have noted that the machines also have a ridiculously high false alarm rate:

The weekly, Welt am Sonntag, quoting a police report, said 35 percent of the 730,000 passengers checked by the scanners set off the alarm more than once despite being innocent.

The report said the machines were confused by several layers of clothing, boots, zip fasteners and even pleats, while in 10 percent of cases the passenger’s posture set them off.

[….]

In the wake of the 10-month trial which began on September 27 last year, German federal police see no interest in carrying out any more tests with the scanners until new more effective models become available, Welt am Sonntag said.

I would argue that this is actually worse than useless, in that providing a significant number of false positives makes it much, much harder to spot the actual positives. It desensitizes agents to assume that any alarm is a false alarm.

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Comments on “German Police Admit That Full Body Naked Airport Scanners Suck; 35% False Alarm Rate”

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35 Comments
FormerAC (profile) says:

more than once?

“The weekly Welt am Sonntag, quoting a police report, said 35 percent of the 730,000 passengers checked by the scanners set off the alarm more than once despite being innocent”

How many set it off only once, despite being innocent?

“they trigger an alarm unnecessarily in seven out of 10 cases”

Is that seven out of ten passengers screened set off an alarm unnecessarily? Or only that 70% of the alarms are false alarms?

AdamBv1 (profile) says:

Re: more than once?

That seems to be what I’m reading.

“Their biggest drawback is the so-called alarm rate. It lies, as it says in the “Welt am Sonntag” this confidential report, at 70 percent. In other words, in two out of three controlled passengers struck the detector.”

http://translate.google.com/translate?hl=en&sl=de&u=http://www.welt.de/politik/deutschland/article13516870/Der-Pannenscanner-viel-Kleidung-viel-Alarm.html

aldestrawk says:

Re: more than once?

Unless, this is being misreported by the media, a false positive rate is a percentage of all passengers screened and is independent of the rate of terrorists bringing weapons or explosives on board. There should be very very few true positives and unless they are an intentional test, the discovery will be publicized.

freak (profile) says:

Re: Just like the alarms at the exit doors of Wal-Mart

With the wal-mart here, it’s because the employees are not allowed to accuse the person of stealing, indicate they might be stealing, or even confront someone they think might have set the alarm off by saying: “I think you might have set the alarm off”.

I have no idea why they even have an alarm if they’re not allowed to do anything about it …

Joe Publius (profile) says:

Re: Re: Just like the alarms at the exit doors of Wal-Mart

As a former retail drone, I get the impression that all of the precautions taken against shoplifing are essentially security theater.

You really can’t accuse someone of stealing, but the alarms, the aisle walks, etc exist to give lifters the impression that they are being watched.

freak (profile) says:

Re: Re: Re: Just like the alarms at the exit doors of Wal-Mart

With any other store I’ve been to, they actually do use those features to catch AND charge people.
Strangely enough, it doesn’t hurt business to kick out those folks who were costing you money every visit. Who knew?

It doesn’t surprise me that wal-mart has such a high shoplifting rate . . .

Richard (profile) says:

Re: Just like the alarms at the exit doors of Wal-Mart

The exit doors at Wal-Mart have a scanner that rarely goes off, but when it does, the employees often times just go over and reset the alarm without checking the person who set it off. Seems there are enough false alarms they consider every alarm a false one.

This is also what happened at Chernobyl.

Anonymous Coward says:

Well, now, let’s see. 35%? I would have to imagine that the machines have some parameters for tuning, and perhaps the German units are set to be very sensitive. Are you sure the US units are used the same way?

What are the standards for a false alarm? The unit blocking an area for further checking? Hmmm, that sounds more like “areas that the machine can’t accurately check that require manual inspection” rather than a false alarm.

Is there like lights and a siren and stuff, or just an operator going “check this person some more”?

Mike, I know you want these machines to go away, but can you please at least try to not over-hype everything negative you read about them?

AdamBv1 (profile) says:

Re: Re:

It basically means that 70% of the people who pass through these scanners get a false positive and since they say that 35% of the people passing through these scanners set off multiple false positives it seems the immediate recourse to a positive scan is another dose of rads. Once you get that second false positive it would seem you get a manual pat down.

Anonymous Coward says:

Re: Re:

What are the standards for a false alarm? The unit blocking an area for further checking? Hmmm, that sounds more like “areas that the machine can’t accurately check that require manual inspection” rather than a false alarm.

That’s the same thing as a false alarm as the machine identifies suspicious items or areas. It’s not a “bomb” or “gun” detector, it’s a detector of odd stuff.

Regardless, the machine is looking for something that is present on a very small fraction of the people checked. If it identifies 1:3 as being possible violators, it is useless. False alarm rate is very important for sensors/detectors, especially those looking for rare things. Almost every single person who sets the machine off is innocent, so the alarm means nothing.

BeeAitch (profile) says:

Re: Re: Re:

So, you’ll happily give up some of your rights as long as you’re not asked to give up all of them.

Then, by your argument, your rights can be stripped until you only have one right left.

The million-dollar question: Which right do you choose to keep? (And do you really believe that you’d be allowed to choose?)

I don’t like you world…

Hans says:

Re: Re: Re:

“Yup, they just use techniques that would violate pretty much all of the US constitution,…”

Citation please.

“… plus large guns on board most of their flagship airlines flights.”

Sounds like an excellent deterrent.

“Yeah, somehow I think a pat down is better than giving up all my rights.”

Yeah, somehow I think that there’s no reason for me to lose my rights in order for you to have the illusion of security. If you’re worried about flying, then don’t fly. But don’t expect all the rest of us to get scanned or groped so you can feel better.

Leo says:

Re: So if there are false positives . . .

Well…
If I remember correctly, only one terrorist attempt has been made in a plane since the porn-scanners are in use. This terrorist was captured on the plane, not by the scanner.

Terrorists might have been captured by the scanners before boarding the plane. But I never heard about this. And whatever the number, it is vanishingly small compared to the number of normal passengers just flying from A to B.

The number you are looking for is either 100% or incomputable.

Jeffrey Nonken (profile) says:

Makes me think of store security scanners...

You know, those silly things they put on either side of the door that beeps when it sees a security strip that hasn’t been zapped? It’s funny to watch the clerks in a store when the alarm goes off — they don’t even look up. Somebody could be taking the entire liquor aisle and they wouldn’t notice.

“The Boy who Cried Wolf” is more than 2500 years old and is embedded in our culture, even to having its own idiom, and we haven’t figured it out yet. Well, it looks like the Germans have. I guess we’re not as smart as they are.

steve2 says:

The scanners give off radiation which makes them a health risk. We aren’t being kept safe if we’re being hit with radiation. There’s already a million sources of radiation in society. Cell phones, laptops, and flatscreens are a few sources. There’s many others. We don’t need these scanners that aren’t even reliable to damage us with more radiation.

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