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Will London Monetize Wifi Tracking Data From Its Tube Passengers? (gizmodo.co.uk) 90

Posted by EditorDavid from the down-the-Tube dept.
New questions are arising about how much privacy you'll have on London's underground trains. "For a month at the end of last year, Wi-fi signals were used to track passenger journeys across the network," writes Gizmodo. "The idea is that as we travel across the Tube network, Wi-fi beacons in stations would detect the unique ID -- the MAC address -- of our phones, tablets and other devices -- even if we're not connected to the Tube's wifi network." The only way to opt-out is to turn off your phone's Wi-Fi. An anonymous reader writes: London is struggling with the transport network capacity so the ability to learn commuters' travel patterns is compelling... Now it emerged that TfL, the operator of London Subway system, is planning to use the system to monetize passengers' data. TfL is also not ruling out sharing the data with third-parties in future.

More information shows that the privacy protection could not be as good as TfL maintains, with reversible hashing and options of giving data to law enforcement. A privacy engineering expert points out additional issues in pseudonymisation scheme and communication inconsistencies. Final deployment has been initially scheduled to start in end of 2017.
"Once the tools are in place, there will inevitably be a temptation to make use of them," warns Engadget, raising the possibility of the data's use for advertising -- or even the availability to law enforcement of location data for every passenger.
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Will London Monetize Wifi Tracking Data From Its Tube Passengers? More

Will London Monetize Wifi Tracking Data From Its Tube Passengers?

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  • With 48bits and the number of people connected at one point to a wifi AP, wouldn't it be possible to randomize the MAC address ? Even with a thousand connected people, which I think could never occur, the rate of collision would be less then 1 in a hundred billion. I think nowadays most chips allows changing the mac, but I'm not sure about wireless mobile chipsets.
    • Yes this is what most phone do (at least Iphone for Android not some much luck), they don't provide the real Mac address to network you don't connect to prevent this kind of attack (they randomise your mac address). The only way for it to works will be that you connect to a TFL owned network where your Mac will appear.That's why so many shops would like to give you free Internet access through wifi, that's the best way for them to track you. However it seems that recently a new attack has been published to

      • Re: (Score:2)

        by gl4ss ( 559668 )

        android has this option built in... basically any new android phones should have it unless operator or someone does something to disable it.

        if you're not using their wifi then though.. why keep it even on or connect to them or have it advertise it's existence.

        whats more weird about getting a fit about this is that uh dude, they already have data about where you got on and got off the tube.

    • Re:Randomize Wifi MAC ? (Score:4, Informative)

      by jargonburn ( 1950578 ) on Monday October 02, 2017 @04:10AM (#55290925)
      Unless things have changed since I last read up on this issue, there are two basic problems with using randomization of MAC addresses to defeat tracking:

      --Software Implementation--
      Lazy method of randomization. Sometimes as simple as incrementing the value of the MAC address by 1, repeatedly over time.
      There are other signatures transmitted besides the MAC address that make it trivial to identify most smartphones, especially given the previous point.

      --Hardware Implementation--
      Smartphone chipsets handle low-level control frames in a manner that is vulnerable to tracking. As in 100% success rate. IIRC, this will happen even if you have the WiFi off in software or are in Airplane Mode.


      Source [arxiv.org]

      • Re:Randomize Wifi MAC ? (Score:5, Interesting)

        by AmiMoJo ( 196126 ) on Monday October 02, 2017 @06:50AM (#55291189) Homepage Journal

        Why would the chipset handle wifi packets when the wifi receiver is turned off? And even if it did, with the transmitter turned off how would the tracker ever know that it did? There is no energy going to the transmitter, no energy radiated.

        Perhaps you are referring to some Apple devices where the off switch doesn't actually turn the wifi off, but most devices don't have that fault.

        There used to be an issue where devices would broadcast the SSIDs of networks they knew about. That was to handle networks that didn't broadcast an SSID themselves, but it's mostly been deprecated and was one of the reasons that MAC address randomization was introduced.

    • iPhones have been randomizing MAC addresses for several years now, specifically to defeat drive-by tracking efforts of this sort (though the examples people were giving back when the feature was introduced were restaurant franchises and the like using their free hotspots to recognize people driving by or stopping in on a daily basis). Once you actually connect to a network, it'll give that network your actual MAC address, but up to that point it simply delivers fake addresses.

      On the Android side of things,

    • I'm not sure about wireless mobile chipsets.

      I've yet to own a phone that I couldn't change the MAC address on.

  • Overcomplicating matters (Score:5, Insightful)

    by andrewbaldwin ( 442273 ) on Monday October 02, 2017 @02:57AM (#55290749)

    I can sympathise with TfL's stated aims - knowing how many people go from place A to place B via route C at certain times of day is useful and can be socially beneficial if it helps train scheduling.

    But this can be done in a simpler way (albeit not in real time - but is that really necessary?).

    Many years ago I recall using the metro and local trains in Copenhagen when they were doing a survey. When you entered the station they gave you a paper slip with the station name and timeslot written on it; when you reached your end destination there was a bin to drop the paper slip into. That's it from the passenger viewpoint - minimal inconvenience and no linking to you as a person (and you could even opt out by keeping the paper slip if you were so minded).

    I'm guessing that at the end of the day they collected the slips at each station and could work out just how many people went on each journey within hour long blocks.

      I do recall thinking that a bar code or QR block would simplify the counting process.

    But that's not cool enough - it's too simple for today's management to consider (and it cannot be subverted or surveilled).

    Slightly off topic - doesn't everyone turn off the phone wifi & bluetooth when not in use? -- doing so seems [in my experience -YMMV] to extend the time between charges by quite a useful margin.

    • Re: (Score:1, Insightful)

      by Anonymous Coward

      they have all of the information on how people are moving across the whole transportation network already - via the Oyster (contactless transport ) cards. So that's a BS aim of tracking.

      • Re:Overcomplicating matters (Score:5, Insightful)

        by oobayly ( 1056050 ) on Monday October 02, 2017 @03:30AM (#55290823)

        The reason they did this was to track people's routes through the system - Oyster will only give the end points, not where they changed stations. The Gizmodo article explains that, if you bothered to read it...

        The Register [theregister.co.uk] did an article on this a few weeks ago and mentions that TFL did a good job anonymising the data:

        Fortunately, TfL did it right: they used ICO guidelines to protect users' privacy by grabbing and tracking MAC addresses and then depersonalized them using a salt which then discarded at the end of each day. That in effect makes it impossible to know what the original MAC address was.

        • And then pretty soon they'll get some more great ideas, like: "are the people traveling on Wednesday the same ones as those traveling on Thursday?". So they'll stop discarding the salt and there goes your anonymity.

        • Re:Overcomplicating matters (Score:5, Interesting)

          by AmiMoJo ( 196126 ) on Monday October 02, 2017 @06:44AM (#55291185) Homepage Journal

          Maybe not... https://blog.lukaszolejnik.com... [lukaszolejnik.com]

          Aside from TfL's apparent confusion of various technical terms, it looks likely that the salts could be recovered. MAC addresses are not random, they are assigned in blocks to manufacturers. Some devices do randomize them, but some don't and it appears that they use only one salt per day for every MAC address they hash.

          You can assume that there will be a large number of devices running wifi chipset X and not randomizing. That gives you a way to check a salt for validity, i.e. if when combined with known MAC addresses from the ranges allocated to that manufacturer it produces a hash in the TfL dataset. And you can further narrow this down by taking your own device with a known MAC address onto the tube during the test.

          It's probably fine... But their lack of technical clarity and secrecy about the scheme they used (for all we know the salts could have just been the date or something silly) isn't very encouraging. As a branch of government they should set the gold standard for this stuff.

      • Oyster doesn't identify the passenger who paid cash.

    • Re: (Score:2)

      by Z00L00K ( 682162 )

      But they don't really know which way people want to go, they will just know the route they take that they think is the best for them.

      What you need is a bigger picture. Looking only at those that uses public transportation and not everyone gives a skewed view. You don't capture routes where there's a need only routes that are congested.

      Drop analyzing the flow in the pipes, look at the end points of people as a group. Clumping together travel routes for people based on where they are at fixed times as a group

    • Re: (Score:3, Informative)

      by michelcolman ( 1208008 )

      Slightly off topic - doesn't everyone turn off the phone wifi & bluetooth when not in use?

      We do, but Apple just turns it on again [apple.com] when we travel to a new location or in any case at 5am.

      (unless we go out of our way to disable it in the system settings rather than through the more convenient control center which tricks us into thinking it's the same thing)

      • Actually, iOS already (since iOS 8) randomizes the MAC address used for scanning. So unless you are actually joined to TFL's AP (or they are intentionally trying to probe each phone with an RTS) the address changes periodically to a new unique value.

        Interestingly, this actually lets TFL get useful information about waiting times at various stations and who transfers where. They just can't track any individual reliably.

    • Many years ago I recall using the metro and local trains in Copenhagen when they were doing a survey.

      The entire article seems to be pointless. London's metro system is electronically gated. They can easily track how passengers are moving between stops using their Oyster cards.

      Slightly off topic - doesn't everyone turn off the phone wifi & bluetooth when not in use? -- doing so seems [in my experience -YMMV] to extend the time between charges by quite a useful margin.

      I haven't done this since the first generation of smartphones. Especially Bluetooth I find makes zero difference to my battery life, and WiFi makes only a marginal difference compared to e.g. being in a low coverage zone and having the LTE radio blasting at full power trying to get a signal. In many cases if you're in a low coverage a

      • There are multiple ways to get from A to B once through the barriers, which means the actual routings taken aren't captured, just the duration and the entry and exit points.

        I can see why TfL want to do this. They do a lot of trickery with signage at peak times to force people flows between platforms etc for better crowd management etc (there are routes between certain platforms at certain underground stations where the "advertised" routes at peak take you on a 3 or 4 minute walk, when actually you can go a

    • doesn't everyone turn off the phone wifi & bluetooth when not in use? -- doing so seems [in my experience -YMMV] to extend the time between charges by quite a useful margin.

      You seem to forget that 99.9% of people who use technology, have no clue at all about technology.

    • I can sympathise with TfL's stated aims - knowing how many people go from place A to place B via route C at certain times of day is useful and can be socially beneficial if it helps train scheduling.

      Surely they can, you know, look at the trains.

    • Re: (Score:2)

      by tlhIngan ( 30335 )

      I can sympathise with TfL's stated aims - knowing how many people go from place A to place B via route C at certain times of day is useful and can be socially beneficial if it helps train scheduling.

      But this can be done in a simpler way (albeit not in real time - but is that really necessary?).

      Many years ago I recall using the metro and local trains in Copenhagen when they were doing a survey. When you entered the station they gave you a paper slip with the station name and timeslot written on it; when you

  • The price of the London tube passes has grown at rates well above the inflation rate for more than 10 years now.

    If some of the money made from WIFi tracking will go towards slowing down the price hikes, I would approve. But we all know that the fare prices will keep increasing faster than the inflation rate "as long as the market can bear it". Only when the passengers will all bike to work because they cannot afford the tube rides will the increases slow (or who knows, even stop)

    And the money made from _pub

  • Now that even supermarkets and other places are tracking customers via wifi as they walk around stores, it makes sense to have wireless turned off everywhere except where you need it on.

    Wifimatic or similar can do this for you. It can save your battery too.

    https://play.google.com/store/... [google.com]

    (I have no connection to this app - I just use it and find it helpful)

  • Sigh (Score:4, Insightful)

    by ledow ( 319597 ) on Monday October 02, 2017 @03:21AM (#55290795) Homepage

    Paranoia much?

    Pretty much if you're on a train (especially a Tube train) then you bought a ticket from A to B or - in London - you bought an Oyster card which records your every journey as you have to tap-in and tap-out.

    This is quite normal for any train/subway system. What information do you think they are going to glean from Wifi that they can't glean in this manner about travel patterns? Only what you give them, and only of little use (does it REALLY matter that the guy going from Embankment to Mile End did a DNS lookup for slashdot.org, and how on earth would you ever properly correlate that if he only quickly checks a website at stations he never alights at, and then turns Wifi off?).

    This is the "machine learning" rubbish all over again. Masses of data, lots of processing, no more insight into anything useful over and above monitoring ticket sales which you have to do anyway.

    • Re: (Score:2)

      by MartinG ( 52587 )

      > This is quite normal for any train/subway system. What information do you think they are going to glean from Wifi that they can't glean in this manner about travel patterns?

      If there is no additional information to be gleaned, why would they bother installing all this wifi tracking stuff in the first place?

      (Also, they are not recording things like DNS lookups)

      • Re: (Score:2)

        by Malc ( 1751 )

        Oyster only tracks in and out points, and possibly some transit points if people use the pink card readers to show they avoided zone 1. It doesn't show exact route and where you dillied and dallied waiting for a bad connection (Overground trains at Wilsden Junction and Piccadilly Line trains at Turham Green, I'm looking at you).

        • Re: (Score:3)

          by ledow ( 319597 )

          Are you seriously suggesting the TfL, the people IN CHARGE OF THE TUBE NETWORK, can't come up with a number for how busy stations are at certain times of the day, but think that Wifi numbers (which by far do not represent actual passenger numbers) will help them do that?

          Really? I mean, I knew they were incompetent, but that would just be staggering.

          The control rooms can see cameras of almost every platform on almost every Tube station. They show it off when they do those documentaries where they cry about

    • Re: (Score:2)

      by Calydor ( 739835 )

      They can reverse-engineer your MAC address, as mentioned in the summary, and continue to track you through the city into these supermarkets. Now they don't just know that you went on the train to get to downtown London, but that you did so specifically to go shopping at a furniture store.

      • Not sure which "they" you mean -
        TfL? they have no access to the wifi data outside of their physical infrastructure. If you are unclear about what that is then perhaps you might want to reflect on one of the names the system is known by, the underground. The wifi signals will not reach into retail premises unless they are within the station.
        You could of course be referring to the company that is contracted to provide the wifi service (is this still O2? I can't be bothered to look it up) but then it relies on

    • Paranoia much?

      Pretty much if you're on a train (especially a Tube train) then you bought a ticket from A to B or - in London - you bought an Oyster card which records your every journey as you have to tap-in and tap-out.

      This is quite normal for any train/subway system. What information do you think they are going to glean from Wifi that they can't glean in this manner about travel patterns?

      Travel patterns are not the gold mine here. Browsing habits are.

      Gathering browsing habits of people who spend XX hours every week in the tube is worth more than you know. Putting ads in front of your eyes for that entire trip is valuable to a lot of companies, since they know you spend 95% of that time staring at a phone screen.

  • ... does not compute.

    Not really news.

  • But if they will admit they're doing it or not.

  • What good is the data? (Score:3)

    by mveloso ( 325617 ) on Monday October 02, 2017 @04:05AM (#55290917)

    Really, once the data is anonymized it becomes useless to advertisers. So the fears here are pretty overblown.

    • Your comment translates as: If they anonymize the data they can't make money selling it.

    • once the data is anonymized

      Never believe any claims that data is "anonymized". Even if they are making a best effort an anonymization, doing so in a manner that actually works and doesn't destroy that value that you're collecting the data for is an incredibly difficult task. I am unaware of anybody who has successfully done it yet.

  • Huh? WiFi? (Score:3)

    by thegarbz ( 1787294 ) on Monday October 02, 2017 @04:36AM (#55290979)

    The London tube and public transport in general was an early adopter of electronic ticketing. What purpose could they have tracking passenger's via MAC address when they can already track them via Oyster card? What are they hoping to achieve via this? Evidence that people are walking down the tunnels?

    It would seem that if you know where a person gets on, gets off, and where your carriages are a simple bit of data analytics could get them the same information.

    • The London Underground is a mass of interconnecting lines, and you can literally enter into the system at 7am and exit at 7pm, having travelled the entire network without exiting the system once - the point of capturing this data is not to see where they get on and get off, its to see what routings they take between those points - that is a wealth of data TfL can use to improve the service.

      • The London Underground is a mass of interconnecting lines, and you can literally enter into the system at 7am and exit at 7pm

        Yes but would you. I mean if the purpose for this is improving the flow of commuters then you'd focus on the shortest time and scheduled path between any two stations. Consumers on average aren't stupid enough to want to spend any more time in the tube than absolutely necessary. Whether someone has fallen asleep on the line, or is going around in a circle really shouldn't matter for any of their scenarios.

        • I mean if the purpose for this is improving the flow of commuters then you'd focus on the shortest time and scheduled path between any two stations.

          But that might not be what the people are doing. At all.

          For example, during my recent vacation in Munich I would often enter the system at Marienplatz, ride to Karlzplatz Stachus or Hauptbahnhof, then ride back out to Isartor. For those who don't know the system, that's getting on in the center of the city, going west, then going back east. I did that almost every day. Now, Munich does not track riders by ticket because you don't need to show anyone or any machine a ticket. At most you stick a paper ticket

    • For the same journey on the tube, there are often several different routes. One of my regular journeys could be traversed over three practical routes (plus countless stupidly long ones). My preferred option isn't actually the quickest - it's about 2 or 3 minutes slower than the obvious/optimum route - but I choose it because during the summer the trains on that particular line are cooler

    • The Oyster card only tells you which which entrance someone came in and which exit they went out. Using the WiFI MAC you can determine routes and train taken and follow walking routes through station.

      When there are multiple routes a passenger might take this information can be used to suggest less crowded options, shows station designers if they have inappropriately sized facilities for the spot demand, etc.

      Here is the reports on the kind of results they got: http://content.tfl.gov.uk/revi... [tfl.gov.uk]


  • Facebook does it. All those tiny like buttons on every page you go to.

    Android helps improve your location tracking by combining wifi AND GPS through google maps...or anything with app rights on your phone.

    In fact so many different organisations do it without explicit consent by cross referencing data, why would it matter if the TfL does it as well?

    Here's the curious thing. Most tube passengers already use an oyster card. (some RFID-ed plastic to pay toll barriers) - so TfL already has movement and tim
  • You missed the word at the beginning of the title of this article. That word is How.

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