Stealing ATM Pin Numbers Using Thermal Imaging Cameras

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Now this is a really neat bit of hardware hacking, it’s been a while since we’ve reported on any kind of ATM Skimming or ATM Hacking stories.

You may remember back in November 2010 – European Banks Seeing New Wave Of ATM Skimming or way back in 2008 when Pro ATM Hacker ‘Chao’ Gives Out ATM Hacking Tips.

The latest is this neat hack that came out of a method outlined by Michal Zalewski back in 2005:

Cracking safes with thermal imaging

Security researchers have found that thermal cameras can be combined with computer algorithms to automate the process of stealing payment card data processed by automatic teller machines.

At the Usenix Security Symposium in San Francisco last week, the researchers said the technique has advantages over more common ATM skimming methods that use traditional cameras to capture the PINs people enter during transactions. That’s because customers often obscure a camera’s view with their bodies, either inadvertently or on purpose. What’s more, it can take a considerable amount of time for crooks to view the captured footage and log the code entered during each session.

Thermal imaging can vastly improve the process by recovering the code for some time after each PIN is entered. Their output can also be processed by an algorithm that automates the process of translating it into the secret code.

The hack works extremely efficiently on ATMs using plastic keypads, it will not work on metal keypads and this method works up to 60 seconds after you’ve used the ATM.

I’m not sure about you guys but all the ATMs I’ve seen here are using metal keypads, so it wouldn’t work too well over here.

Either way it’s a fairly cool hack and I’m glad to see, so far there’s no proof of thieves using it in the wild.


The findings expand on 2005 research from Michal Zalewski, who is now a member of Google’s security team. The Usenix presenters tested the technique laid out by Zalewski on 21 subjects who used 27 randomly selected PINs and found the rate of success varied depending on variables including the types of keypads and the subjects’ body temperature.

“In summary, while we document that post-hoc thermal imaging attacks are feasible and automatable, we also find that the window of vulnerability is far more modest than some feared and that there are simple counter-measures (i.e., deploying keypads with high thermal conductivity) that can shrink this vulnerability further still,” the researchers wrote.

I wonder if we’ll see a spate of real life attacks based around this technique now the paper has been published publicly.

You can grab the paper discussing the technique here: Heat of the Moment: Characterizing the Efficacy of Thermal Camera-Based Attacks [PDF].

Source: The Register

Posted in: Hardware Hacking, Privacy

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10 Responses to Stealing ATM Pin Numbers Using Thermal Imaging Cameras

  1. phed August 24, 2011 at 6:10 pm #

    they still only know the 4 digits and need to guess the correct combination do they not?

    • Kevin Flynn August 24, 2011 at 7:32 pm #

      Not really… the keys would be warmer or cooler depending on which was pressed first.

      • Syaz August 26, 2011 at 10:32 am #

        Good thing my habit is to use at least 3 fingers pressing the pins…

  2. Kevin Flynn August 24, 2011 at 7:30 pm #

    Given that the method relies on the keys retaining heat, you could solve the problem of metal keys with a simple hack.. apply some PVA [school] glue to the keys, and wait. The glue dries clear and creates a thermal barrier. Problem solved.

  3. Dan Glass August 24, 2011 at 10:45 pm #

    wouldn’t how hard they pressed or duration affect the residual heat? what if I paused on the first two but just tapped the last two? in any case most people probably press all four in a similar way (strength and time) so if the subtle differences between fractions of a second can be detected i buy this working.

    • Darknet August 25, 2011 at 9:44 am #

      That would make a difference, but most people would hit the buttons with a regular cadence. The time difference between each button does register a slight difference on the thermal scan allowing the software to predict the order as well as the keys pressed.

  4. CyberNinja August 25, 2011 at 12:20 pm #

    Does the difference then also take into consideration if I withdraw an amount that I punch in on the keypad aswell?
    Depending on the PIN that could create some additional heat signatures.

  5. Born2BFree August 25, 2011 at 3:19 pm #

    Just holding your hand over the keys “warming them” should solve the problem, Before and after.
    B2B

    • Headroller September 1, 2011 at 1:06 am #

      Or just swiping your fingertips over the keys afterwards, 1/2 second on each row should do it. Interesting hack though, must be a fairly sensative thermal camera to tell the difference.

  6. Bogwitch August 26, 2011 at 9:38 pm #

    “I wonder if we’ll see a spate of real life attacks based around this technique now the paper has been published publicly.”

    I think it is unlikely. There is little reward for the skimmers to invest in the technology to facilitate this. They are far more likely to rely on the low hanging fruit, those cards that they can capture easily. The ATMs used outside banks, etc – normally associated with skimming devices almost always have metal, vandal resistant keys – http://goo.gl/6pNt7. The ones installed in shops etc are more likely to have the plastic keys.