TSA doesn't understand what "random" means

Deirdre Walker, the 24-year police veteran and former Assistant Chief of the Montgomery County, Maryland, Department of Police who wrote up a sharp, professional critique of the TSA's checkpoint procedures, has written a follow-up, showing a huge flaw in the "random" screening process used at the BWI airport:
I asked, "How are people selected for secondary searches?. She replied "It's random."

I asked "Is there a mark on my boarding pass?" She replied, "We used to do that, but we don't do it anymore." She did not know why that practice had been discontinued.

I stated "So you look at people as they are entering the metal detector, you make some type of assessment, and then you select people for secondary searches, right?"

...At this point, I turned to look over my shoulder and observed a Caucasian woman in her late thirties or early forties standing inside the whole-body imager. I called my screener's attention to this and said. "Look over there. There's a woman in the scanner. You all picked me for a search, and then the very next person you select is a woman. Why didn't you pick a white guy? Where are all the white guys?"

She replied, helpfully, "We are understaffed today and we don't have enough male screeners to do pat downs. We are not allowed to do opposite sex pat-downs so we are only selecting women for secondary screening."

By this point, I was seated and she was patting down the bottom of my feet. The secondary search, more thorough than the last search I had been subjected to in Albany, but equally ineffective, was nearing completion. I said "If you are only selecting women, how is that random?"

She said, "You're done. You can collect your belongings, Have a nice day."

"Where are all the white guys?" -- Update on "Do I have the right to refuse this search."


  1. I hate airport security as much as the next guy, but seriously, this is just a joyride on the outrage bandwagon.

    It well known (citation needed) that humans poor sources of random, do (presumably) random staff shortages make the process somehow less random?

    And hey, it’s not like security checks actually catch terrorists.

  2. What gets me is the number of times I’ve gone through security forgetting to finish drinking all the water in my stainless steel water bottle, but since they can’t see through it in the scanner, they don’t even stop and ask about it. When I used to travel with a clear plastic Nalgene bottle, they’d always make me finish drinking it before going through with the empty bottle.

  3. I hate to contradict Ms Walker, as I strongly agree with her view on the abusive and ineffective search procedure, but the selection procedure, as present is still random.

    What it is lacking is not randomness, but ergodicity. As anyone with experience in Monte Carlo method knows, ergodicity is quite more important than randomness to get meaningful results.

    However, the sampling frequency can be skewed, to improve the efficacy of the sampling procedure. E.g. if you know that terrorists are predominantly Caucasian tall well-fed women you can pick more of this kind to improve the efficacy of the random search. Of course it won’t help if the procedure is not based on solid assumptions.

    1. Well that link really helped. (Not)

      “In mathematics and physics, the adjective ergodic is used to imply that a system satisfies the ergodic hypothesis of thermodynamics or that it is a system studied in ergodic theory.”

      Seems a bit self-referential to this non-mathematician. Any mathemamticians here who speak English?

  4. What’s really lacking is brwainz.

    This is important: Next time, observe how many oriental women are selected. Particularly at Heathrow, they suffer from over-selection syndrome – because they are much more likely to quietly comply with the search procedure, allowing the search rate to remain high. Skew!

    Given the observation to which we’re subject as we move through security, I’d love to know what choices are made at what point for search. Obviously, we all know the tech exists for facial recognition.

    I’d say they whole thing is just a charade, but any TERRORISTS reading might get wise to it.

  5. And then when they find our vibrator in our bag, we’re made to stand around and wait while they all play with it and marvel at it and ask each other whether it’s a bomb.

  6. Most people think that random means that identical items should not appear in sequence. Thus a ‘random’ sequence of

    3, 0, 8, 9, 9, 9, 6, 8, 2

    is rated as less random then one without the repeating 9.

    Not that the searches are truely random but brief observations that appear to notice repeated samplings of same elements are probably misleading.

    tl,dr = people have no idea of what is random.

    1. Interestingly, on the show numb3r5, they were investigating some arbitrary set of crimes where things were “too random”, and refered to it as something like the iPod shuffle random which isn’t random because it disallows the same song every being played twice.

      So in effect, 3, 0, 8, 9, 9, 9, 6, 8, 2 could and should be a random sequence.

  7. Oh, come on. As much as I agree that most of TSA’s schtick is Security Theater, this is not an example of a non-random screening in any important way.

    The important question isn’t, “Is the security staff at any given time doing truly randomized search?”

    The important question is, “Is any bias in the pattern of searches predictable and exploitable by a terrorist?”

    If a transient staffing glitch means that only women are being searched for a couple of unpredictable hours, this doesn’t translate to an exploitable example of non-randomness.

    1. I think you’re contradicting yourself, derPlau:

      The important question is, “Is any bias in the pattern of searches predictable and exploitable by a terrorist?”

      If a transient staffing glitch means that only women are being searched for a couple of unpredictable hours, this doesn’t translate to an exploitable example of non-randomness.

      The exploit seems obvious to me.

      The fact that only women are being searched is apparent enough that Ms. Walker noticed it after a few minutes.

      So all you have to do to exploit it is send through male operatives during those times.


      1. Are you trolling? You quoted his second sentence, but did you actually read it?

        He’s not saying that “we only search women” is unexploitable. He’s saying that a spontaneous decision to only search women, for a couple of hours, and then go back to the regular “search everybody” system, is not exploitable by a terrorist who needs more than a couple of hours to plan an attack.

        1. I don’t think Lis Riba is trolling, but rather posing a possible result. Lets say, a terrorist ( i’ll call him bob), reads that article, and thinks “Hey I could exploit that.” So bob gets a job at the airport with the TSA and studies their schedules and patterns. And after a few months he has a lot of data, from which he finds the best time to slip materials through the TSA check point.

          He calls the terrorist pals, joe, ed, and toby, and tells them when to go board the plane. Hence joe, ed and toby get ignored becasue the TSA doesnt have enough screeners to check male passengers. Then they blow up the plane or do what ever else they want to with the plane, and everyone bemoans “how could the TSA let this happen?!”

        2. I agree that Lis Riba isn’t trolling, and I’d recommend reading comments more carefully before leveling such a charge.

          Lis Riba’s comment isn’t even that the terrorists need to infiltrate the TSA. Rather, if it is known that there are occasional, random periods of a few hours during which one sex won’t get properly screened, and such periods are immediately visible to the general populace (as we know from the article), then they can hang around with their bombs, wait until such a time (most screening lines are visible from pre-ticket areas), buy a ticket, and have an increased chance of getting though unmolested. If no time appears, don’t buy a ticket and try again another day.

  8. That is so interesting. When I fly, I see a lot of “random” checks of middle-aged women. So many that I’ve concluded that the TSA agents are just as afraid of confrontation as anyone and were approaching people they perceived as less likely to be aggressive about being searched.

    I also think TSA has become a LOT nicer in the past year. I don’t know why we still have one. But, at least they’re cuddlier.

  9. for the love of god, how much more of this is going to happen before we finally revise an obviously flawed system?

  10. What’s particularly stupid is the same-sex pat down policy. What if the TSA agent is homosexual? What if the passenger is?

    Or is there some other problem with opposite-sex pat downs I’m missing?

    1. I wonder what would happen if a male requested to be patted down by a female agent, or if a female requested to be patted down by a male agent. Are they reasonable requests and, more important, would the TSA comply with the request?

      Next time I’m being patted down I’ll ask them to go a little more…slowly…oh, yeah…

      1. I wonder what would happen if a male requested to be patted down by a female agent

        The local beauty parlor has a big sign that says, “We Don’t Do Brazilians On Male Customers.” Extrapolate from that.

  11. derPlau… That’s actually highly exploitable non-randomness. People tend to work the same shifts. If they’re low on male screeners today, that probably means that they are low on male screeners on a regular basis. Maybe because one guy is sick a lot, maybe because their diverse workforce rules don’t allow them to consider gender in making assignments, so that checkpoint has a statistical imbalance of women working it. This is the type of pattern which is easily revealed through surveillance over time. You watch, you learn, you wait. Remember, the staffing at the checkpoints can be viewed WITHOUT going through security. Anybody can just buy a cup of coffee and sit all day and watch and take notes.

    Then, at the right time, you send Achmed through with the plastic explosive strapped to his body, knowing that as a man, he won’t be searched that day.

    Even if it is a fairly rare occurrence, it’s still an exploitable weakness. You show up with a team of terrorists planning to take over the airplane. You bring at least one woman with the team. You check the various security checkpoints and see which one is uni-sex for the day (or for those few hours). If it’s all male, you strap the explosives on the girl. If it’s all female, you strap the explosives on one of the guys.

  12. What the TSA is doing is really arbitrary searches, not random. And in any arbitrary system dictated by humans, subconscious bias plays a role, and thus can be exploited by someone willing to find the patterns. They might as well not be doing any searches at all. It’s about as effective as what they’re doing now.

  13. The searches aren’t done competently anyway, despite all the expensive technology and all the fear mongering, so it hardly matters whether they are random or not.

    I think the whole and entire point is a ritual humiliation of the citizen, to enforce the proper attitude of cowed subservience to those who are above the law, and provide an excuse to isolate or inconvenience those unwilling to submit.

    1. interesting idea. a civic lesson in what it’s like to not have privilege, perhaps it’s worthwhile after all.

    2. You are correct sir! You have keyed in on a behavior that human beings are apt to do; conform. Even as children we are taught to conform, that being different is bad. Hell, I think most animals with social behaviors conform, if only to survive; conform to behavior, conform to looks, etc… Being different means you are singled out, being singled out is bad, and that could very well mean whether or not you survive another day.

      So you threaten them with being singled out, and survival instincts kick in; the populace will fall in line like cattle to the slaughter. Sure there are a few people out of the bunch who have enough guts/ common sense to buck the system, but those few don’t make a difference socially.

  14. I was told to go into the full body screening machine recently. I told the agent politely, “actually no thanks, I’m not prepared to do that.” The look on his face was priceless, then he let me go!

  15. Multiple times I have made it through airport security with live .45 rounds in my carry on, left over from time at my ranch. Not to mention liquids, clippers, etc. Always the same airport.

    OTOH, I flew out of Grand Forks ND, and they found my 5 hour energy, and then tore my luggage apart. Those Scandinavian folks took their job seriously.

    Like all government jobs, it will come down to the people who do the work. In places of high economic activity, those government workers will not be of the highest quality.

  16. I recall flying from Orlando with my elderly parents.

    It was like a scene from a Fellini. Out of the 8 open lines, 5 had senior citizen being wanded almost in perfect synchronization. Had there only been music.

    Why 5? Because two had hip replacements, two had knee replacements, the other had a brace; 3 were decorated WWII Veterans.

    How do I know the veteran status of two strangers? Because I couldn’t help but think how ridiculous this was – so I walked up and asked these elderly gentlemen if they had served – and then thanked them for their service to our Country.

    Made me wonder what potential bad-guy would be able to get through as we pat down grandma and grandpa.

  17. I jsut went through a TSA patdown while carrying a 14month son. My wife was pulled to a office and I was required to turnover 2 bottles of milk and a bottle of juice. They tested it with a litmus smear in a machine. It was frank and amazing at the same time. I thanked them for their professionalism. It part of the job to keep the bad guys guessing. Get over it, and just do what they say.

  18. The TSA procedure is political theater to prove that they are doing something to prevent attacks. The more annoying and harassing, the more effective it will be because the victims will be that much more convinced they are giving up their freedom in a good cause. I once missed a flight because a mentally handicapped man could not understand what was being asked of him and they held up an entire line of people for nearly an hour. Instead of shifting him to another area and doing a secondary search, they argued with him. It was a perfect example of your government in action.

  19. My last time through a screening, the person ahead of me was U.S.Army, in BDU’s. As such, he doesn’t have to take his shoes (combat boots) off. But, the screener had a hissy-fit that this G.I. didn’t have a copy of his PCS orders on him (they were packed in his bag, which had already gone through x-ray), and pulled him aside to dress him down, until a supervisor came over and waved him through.
    As I said to the G.I.:
    Hey, they’re Morons, but they’re our Morons.

  20. I was “randomly” screened because I was the only white guy coming from a layover from Colombia. The security guard asked me how colombia was and i replied, i was only there for a few hours. Since it was a layover from ecuador. The securty marked my ticket and bam. random check.

  21. The really predictable thing about Airport-Kabuki is the search itself. Any serious terrorist can figure out how to get what they need past the screen by watching the staff give a few folks the treatment. That we are still doing shoe searches tells you that it is all form, no function. TSA strategy seems to be based on catching terrorists trying to do what has already failed.

    As far as selecting for scrutiny, I saw a lady with flip flops on complain about the absurdity of having to take off her paper thin, completely open shoes. She got the extra scrutiny. Improper tone, I guess.

  22. I just had a total knee replacement. Can hardly wait to resume my heavy travel routine. I’m sure I will be thrilled at each and every airport I deal with. Yippee!!

  23. A friend who used to work for TSA constantly reported the strange fundie orientation of a large proportion of its employees. Fundies have a strong proclivity towards various types of bigotry such as sexism. They are also cowards who cowtow to power figures in their many manifestations.

    On the flip side, the responses on this page to Walker’s report seem demonstrate the abject opacity of so many nerds that read BoingBoing (the preoccupation for specificity of terminology and numbers, etc). Could it be that so many of this website’s readers are excessively privileged, most likely male, and have NO CLUE as to what it’s like to go through the repeat humiliation and abuse that seems to be more common for women than men thanks to TSA.

  24. All this flows back to the notion that terrorists really want to blow up a plane – hearkening back to the 70’s when (I can’t remember who) blew up planes in the desert – very spectacular. Or the Lockerbie tragedy, which PanAm flight dusted itself televisually into a little village.

    I think they want to kill and scare people, and I put the fact that they don’t manage it down to incompetence, idiocy and ludicrous distance from reality.

    Frankly, I can conceive of hundreds of better, easier ways of doing a few people spectacularly in than attempting to damage an aircraft.

  25. A random process is unpredictable. That doesn’t mean that it is fair. For example, rolling two dice and adding them will give a random number, but the result is most likely to be 7 and will never be a 13.

    So unless they were predictably stopping every single woman at the airport, TSA was indeed behaving randomly. The only surprise is that women were being randomly sampled but not men.

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