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    Will Anyone With a Dot-Matrix Printer Please Hold Up Your Hand

    Source: Dr. Dobbs Journal, Email Update, 2009/Jun/30

    Does anyone still use dot-matrix printers? I don't, and I can't recall the last time I saw one. Wait. I recently bought a replacement brake-light bulb and my purchase receipt was printed out on a dot-matrix printer. And now that I think about it, my bank prints out deposit and withdraw receipts on small dot-matrix printers.

    In fact, say researchers at Saarland University, 30% of the banks surveyed still use dot-matrix printers. Of that number, 29.9% use dot-matrix for receipts like the one's I get, and 83% use them for other purposes. Anyone else? How about doctor's offices? What the same researchers found was that 58.4% of the clinics polled still used dot-matrix printers, 79.4% for prescriptions and 84.5% for other uses.

    But do we really care whether these businesses choose to use technology from an earlier era? We should. Why? Because it is a security issue, at least according to Saarland University's Michael Backes, Markus Durmuth, Sebastian Gerling, Manfred Pinkal, and Caroline Sporleder. What the researchers discovered is that by capturing (recording) the ratta-tat-tat of dot-matrix printers, then applying feature extraction from speech-recognition (Hidden Markov Models) and music processing, you can extract valuable, private data from dot-matrix printers. Little things like your account number, account balance, health issues, and the like. Stuff you thought was private. With permission of course, the researchers successfully mounted an attack in a doctor's office and recovered the content of a medical prescription. According to their paper How Printers Can Breach Our Privacy: Acoustic Side-Channel Attacks On Printers , the attack was conducted under realistic conditions with people talking in the waiting room.

    So why do people still use dot-matrix printers? For all the reasons you'd expect -- they're cheap, durable, and still work with old hardware and computer systems. Consequently, only 4.7% of the doctor's offices and 8.3% of the banks surveyed had plans to upgrade printers.

    My bank account (such as it is) is one thing. But having my brake-light replacements crop up on the Internet is something else altogether. I'm off to alert the auto-parts store.

    -- Jonathan Erickson jerickson@ddj.com

    Abbreviations

  1. TBA::="To Be Announced".
  2. TBD::="To Be Done".

    Also see [ glossary.html ] for more special abbreviations and phrases.

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