Shostack + Friends Blog Archive


TSA Approach to Threat Modeling, Part 3

It’s often said that the TSA’s approach to threat modeling is to just prevent yesterday’s threats. Well, on Friday it came out that:

So, here you see my flight information for my United flight from PHX to EWR. It is my understanding that this is similar to digital boarding passes issued by all U.S. Airlines; so the same information is on a Delta, US Airways, American and all other boarding passes. I am just using United as an example. I have X’d out any information that you could use to change my reservation. But it’s all there, PNR, seat assignment, flight number, name, ect. But what is interesting is the bolded three on the end. This is the TSA Pre-Check information. The number means the number of beeps. 1 beep no Pre-Check, 3 beeps yes Pre-Check. On this trip as you can see I am eligible for Pre-Check. Also this information is not encrypted in any way.

Security Flaws in the TSA Pre-Check System and the Boarding Pass Check System.

So, apparently, they’re not even preventing yesterday’s threats, ones they knew about before the recent silliness or the older silliness. (See my 2005 post, “What Did TSA Know, and When Did They Know It?.)”

What are they doing? Comments welcome.

One comment on "TSA Approach to Threat Modeling, Part 3"

  • Doug says:

    Although I don’t disagree with your points, I think you are missing a larger and more important point.

    Pre-check makes travelers more safe. Today, travelers are much more likely to suffer an adversity in the hands of TSA employees than in the hands of terrorists. Because Pre-Check reduces the contact between travelers and TSA employees, it reduces the frequency of harm. That makes travel more safe.

    The apparent flaw you discuss, if exploitable (e.g. no digital signature in the barcode), will give more travelers the opportunity to reduce contact with the TSA, thereby making their travels more safe.

    The risk is greatest at the checkpoint (theft, unwanted touching, detainment, arrest, etc). Pre-Check reduces that risk.

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