Hacking the Dot-Matrix Printer

It sounds like something out of a bad spy movie, but researchers at Saarland University have published a paper on a new hack targeted at those old trusty dot-matrix printers. These researchers discovered that by recording the sounds the printers made and running them through a speech-recognition algorithm, they were able to extract the words printed on the page.  They were even successful in running their tests inside an actual doctor’s office – with permission of course, so this is not something that only works in the lab.

So what? No one still uses these dinosaurs, right? Not so fast, in a survey conducted by the same university, 30% of the banks, and 58.4% of doctor’s clinics still use them. In many cases, these devices were used to print out semi-sensitive information like receipts and prescription information.

And why do businesses still use dot-matrix printers? Well, for fairly standard reasons – they cost less than more modern printers, are very durable, and work with older hardware and computer systems. One company I talked to about this study said that it was cheaper to keep these old printers working than to upgrade the systems and software that utilized them.

After reading the paper, it seems the attack would have to be tailored to a particular model of printer, but even with that limitation, some interesting possibilities are available. Will the next Mission Impossible movie include a scene with Tom Cruise planting a recording device in a bank to get account numbers of his target? And what will we find out next, that the contents of a CRT or LCD can be replayed by measuring the radiation output? Oh wait….

Original study: How Printers Can Breach Our Privacy: Acoustic Side-Channel Attacks On Printers

4 replies
  1. Mike Wilkerson
    Mike Wilkerson says:

    A really outstanding article and getting some perspective from the sales viewpoint also offers not only how valuable the dot-matrix printer is, but how sought-after they are as well. Two weeks ago on a Thursday morning, there was a frantic call from a man in Ohio, looking for a specific dot-matrix printer – not because the laser printers he had wouldn’t work. Not because there was some requirement to have tractor-fed paper, but because it’s what they’d been using – forever – and they didn’t want to upset a very productive applecart.

    Habits are always difficult to break, but the one “habit” every company, business and organization has in their favor is doing what works for them.

    This guy was willing to get a driver down to get a dot-matrix printer – FROM OHIO.

    Another stark piece of data that confirms the conclusion above. Great piece, Brian. Thanks!

  2. Mike Sweeney
    Mike Sweeney says:

    And if all this wasn’t enough to tell you that Dot Matrix are not antiques, I know of one large organization that spent $30000.00 + to get a laserjet to act like a tractor fed dot matrix printer. Weird world we live in, eh?


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