It's surprisingly easy to alter anyone's airline reservations

Karsten Nohl and Nemanja Nikodijevic's Chaos Communications Congress presentation details their research into becoming a "Secret travel agent": they figured out how to force the various portals to the Global Distribution System to let them know if they've guessed someone's reservation locator code, which they can use to arbitrarily alter your flight plans, sending you to different cities, reseating you, or cancelling your flight.

The GDS has many portals, and many of those are not rate-limited; to make things worse, the space of all possible locator codes is pretty small, since it's non-case-sensitive letters and numbers (excluding 1 and 0, which could be mistaken for the letters I and O). So by sending a lot of guesses to a lot of places very fast, it's not hard to figure out whether any surname has a valid code associated with it.

The codes don't contain ones or zeros to avoid confusion with I or O, Nohl says—they only use upper case letters and no special characters too. On top of that, in two out of the three larger GDSs, the numbers increase sequentially, Nohl explained. This means a hacker can predict when a particular set of numbers are more likely to be used at a certain time of day, or day of the week, in turn making it much more likely that they will successfully match a six digit code with the correct last name, and gain access to flight information.

The codes themselves can also be easily found on people’s' luggage tags or potentially on a boarding pass, as others have previously found.

Armed with these techniques, a hacker might be able to track someone, finding out where they’re flying to and from. Working with the German TV station ARD, the researchers were able to change the flight booking of a reporter, putting him on the same flight as, and in an adjacent seat to, a German politician.

“We were able to try a couple million for a given last name, and that was enough to find this German senator,” Nohl told Motherboard.

lecture: Where in the World Is Carmen Sandiego? [CCC]

It's Incredibly Easy to Tamper with Someone's Flight Plan, Anywhere on the Globe [Joseph Cox/Motherboard]

(Image: Southwest Flight 345 after nose-first crash landing on RWY 4 at LaGuardia 22 July 2013, PD)

Notable Replies

  1. Hi, United reservations desk please? Yeah, this is Sessions, first name Jeff. I'd like to change my flight to Aleppo. Thanks!

  2. ...so that they can greet you at the terminal with an omnipotent air.

    Ah, hello Senator. I suppose you are wondering why I've brought you here today...

  3. I wrote about this vulnerability and told airline reservation companies about it in 2002:
    https://hasbrouck.org/articles/watching.html

    These vulnerabilties could be fixed. But no CRS or airline has ever approached me to ask how they could be fixed.

    Travel companies care about threats to their money, not threats to individual travellers' privacy or security. They will deny this, but their decades of failure to address these well-known and well-publicized vulnerabilities proves that this is true.

    I first wrote about these issues in my book, "The Practical Nomad Guide to the Online Travel Marketplace", published in early 2001, in which I said, inter alia, "Privacy is the Achilles heel of Internet travel planning".

    I have said consistently since then, in print and in many venues, that I believe that commercial and illicit exploitation of PNR data and other travel metadata (metadata about the movement of your physical body, as compared with telecom metadata about the movement of your messages) should be at least as much of a concern as government access to or use of this data.

    But since 9/11, the focus of public and political and media attention has all been on government access to and use of Passenger Name Records (PNRs), rather than on the commercial abuse of this data, and the vulnerability to intrusion and illicit exploitation, that predated 9/11 and has continued unabated.

    If the data protection laws that have been in effect since the early 1990s in the EU and Canada had been enforced, CRSs would have been required to make changes that would have significantly reduced some of these vulnerabilities.

    Mister44 says, "Hackers probably don't have much motivation to do this sort of thing." That depends, of course, on how you define, "hacker". In my experience in the travel industry working with reservations, the most commonly-detected real-world threat to reservation data is by perpetrators of stalking, harassment, domestic violence, and kidnapping or assault in child custody disputes. Those who are detected are usually trying to get access to PNR data through pretexting. (I used to train travel agents to be alert to the possibility of this sort of pretexting.) There could be many other motives for a targeted attempt to get access to info about the travel of a specific person of interest.

    Other attack methods, such as those demonstrated by SRLabs at CCC, are less likely to be detected.

    Mister44 says this is, "something airport security doesn't seem to worry about because it never happens." It would be a mistake to think this never happens. Airlines and CRSs don't worry about it because it doesn;t affect their profits.

    There are no access logs. Each PNR stored by a CRS includes a change log called the PNR "history", but not an access log. So we would be unlikely to know the scope of attacks unless an attacker (a) was caught be other means, and (b) confessed to their mode of attack.

    Airlines and CRSs will act only when either (a) governments order them to do so, and enforce those orders by jailing
    executives who don't comply, or collecting fines large enough to affect executives bonuses and investor confidence in their stock, or (b) public pressure forces them to do so following a scandal when some murderous stalker confesses that they tracked down their former domestic partner and killed them and/or their children through PNR data.

    I hope that (a) comes before (b).

    Answers to more FAQs about this here:

    https://hasbrouck.org/blog/archives/002279.html

  4. i'll take free first class upgrades, ticket refunds, extra mileage points, extra baggage, and comped accommodations please, if any of those things are possible. thanks.

  5. Another argument for disclosing vulnerabilities to the public if they are not fixed after a certain amount of time is that you never know when "bad guys" have discovered the vulnerability. So, eventually it is a service to let the public know that their information may be insecure, and nothing is being done to secure it. This (depending on the nature of the vulnerability, etc), allows the public to make an informed decision about whether they'd like to continue using an insecure product or service. (It also often has the side-effect of motivating some companies that can't be bothered to care about their customers' security to actually do something about it.)

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