back to article German researchers defeat printers' doc-tracking dots

Beating the unique identifiers that printers can add to documents for security purposes is possible: you just need to add extra dots beyond those that security tools already add. The trick is knowing where to add them. Many printers can add extra dots to help identify which device printed a document, as it's handy to know that …

  1. Anonymous Coward
    Anonymous Coward

    Did it really sink Reality Winner?

    Apparently she was only one of six people who had accessed that particular document, and when questioned she admitted what she'd done. So I doubt those dots had anything to do with fingering her, though that makes a good story as a cautionary tale to other would be leakers.

    Seems pretty simple to avoid though - don't give people the actual document you printed on a printer that can be traced back to you. Running it through a scanner at a lower resolution that lose those tiny identifying dots but leave the text and graphics still legible, or if it is 100% text use OCR. If you need paper of some sort print that electronic product on a public printer like at a hotel business center.

    1. Mr Dogshit

      Re: Did it really sink Reality Winner?

      " fingering her"?


    2. Tomato42

      Re: Did it really sink Reality Winner?

      The dots in question are yellow, just use b&w printer, go to some public xerox place to then duplicate them again on a b&w machine, if you are really paranoid.

      1. Anonymous Coward
        Anonymous Coward

        Re: Did it really sink Reality Winner?

        "if you are really paranoid ...... "

        Even with a b&w photocopy text based steganography that uses kerning will still get you caught.

        1. Anonymous Coward
          Anonymous Coward

          Re: Did it really sink Reality Winner?

          Printers don't print text, they print dots. The steganography would have to happen in the driver.

          1. Mike 16 Silver badge

            Re: Did it really sink Reality Winner?

            The printer's laser or inkjets may just print dots, but they are controlled by software in the printer. If it is capable of printing Postscript files (without the host rendering that made "Windows Only" printers such a joy), the (software) render engine in the printer could definitely add the steganography. AFAICT, one could write a "simple" PS program to play chess with the user, by sending each "move" as the full state of the board so far. May not need that for printers with local "font cache" that persists across print jobs.

            And as others note, one could mess with the character rendering or kerning to obviate the need for Yellow Journalism (Ummm, Bacon!)

            I do wonder which countries have made (or about to make) possession of a Brother, Samsung, or Tek printer incontrovertible evidence of Treason.

            Gotta go. There are two gentlemen at the door saying they need to do scheduled maintenance on my Brother laser-printer. Something about my not yet installing the latest firmware update.

          2. Anonymous Coward
            Anonymous Coward

            Re: Did it really sink Reality Winner?

            "Printers don't print text, they print dots. "

            Correct, but you don't normally send dots to the printer when printing a document. You send the document in a page description format (Postscript, PCL5, PCL6 etc.) It contains the text you are printing and information on how it should be printed. PCL5 onwards supports kerning within the printer.

    3. Anonymous Coward
      Anonymous Coward

      Re: Did it really sink Reality Winner?

      The dots were irrelevant? I remember seeing close-ups of the images with (enhanced) dot patterns on day one. You can actually see them all over the images in the Intercept article, particularly the one with a black background. They're faint but clearly not noise.

      According to Wikipedia (FWIW), she left several footprints: the dots; printing the documents from her work PC while logged in as herself; and emailing The Intercept from her own computer.

      She also made the mistake of piling on to a political witch hunt, ironically one masterminded by the old guard of the intel community, it seems. If she'd left it alone, in due time they would've wielded this ammunition against Trump the right way, in the Congressional star chamber. Though let's be honest: it was a damp squib. She accomplished fuck all for her cause, and earned a five year prison sentence for her trouble.

  2. Anonymous Coward
    Anonymous Coward

    Next step. Get the secret printer dotty code of the personal printers of mangement in your favourite spy agencies. Substitute those. Way hey.

    1. Anonymous Coward
      Anonymous Coward

      personal printers of mangement in your favourite spy agencies

      You are not likely to get your mitts on those. Now, printouts from officials' printers - your MPs, your city council's, etc are much easier to get a sample of. In fact, I have quite a few in my document folders.

      1. vagabondo

        Re: personal printers of mangement in your ...

        Your favourite spy agencies may well include such as the Home Office, DWP and your local council etc.

        The problem is that paper communications are rarely printed on the official's desk, but in the mailroom for posting by junior staff. We will have to wait for the home printer code templates for the Home Secretary and PM to be circulated on the intertubes.

        1. BebopWeBop Silver badge

          Re: personal printers of mangement in your ...

          True, but if the dot pattern is related to the source of the document, not just the hosted printer (which would make sense from a security/traceability persepctive then I see some potential

          1. Stoneshop Silver badge

            Re: personal printers of mangement in your ...

            True, but if the dot pattern is related to the source of the document, not just the hosted printer

            It's the printer that adds the dot pattern. Note the mention in TFA that Samsung, Brother and Tektronix printers don't seem to add those dots.

            1. BebopWeBop Silver badge

              Re: personal printers of mangement in your ...

              I'm well aware of that - merely a suggestion that a driver for *any* printer might be able to add the patterns absed on it's source and then thight be augmented by a printer specific code.

  3. Anonymous Coward
    Anonymous Coward

    Textronics - Weird

    The fact that they could not come across a dot does not mean there is no marking. AFAIK Textronics was one of the first to come up with this technique so it may be marking them in a different way (greyscale variation, etc).

  4. Anonymous Coward
    Anonymous Coward


    Doesn't this need an opt-in? ;-)

    1. Elmer Phud

      Re: GDPR?

      nah, this comes under 'security' so is untouchable

    2. phuzz Silver badge

      Re: GDPR?

      Presumably the argument is that if you buy the printer, and hand out print-outs, then it's you spreading your own personal information. Perhaps you could sue yourself?

    3. TRT Silver badge

      Re: GDPR?

      Ghost Dot Printer Recognition?

  5. DropBear

    I have to assume the "additional" dots come manually added to the user data to be printed whereas the "encoded" dots are applied by the printer firmware, which raises a huge question mark about whether "your" dots end up indistinguishable in every way from "theirs". If there's the utterly slightest misalignment in the obfuscating dot pattern compared to the built-in one you're busted; if the yellow is not the exact same shade, you're busted. If the dithered sub-structure of a dot (if any) is in any way different, you're busted. And that's assuming you identified with 100% confidence which template you should use on the printer you're printing on (especially if it isn't even your own). Taking a poor-ish resolution photo of those papers instead of printing them starts to sound better and better (at least as far as anti-dot measures are concerned).

  6. Anonymous Coward
    Anonymous Coward

    So just....

    ...printing on yellow paper is out of the question?

  7. McKrack


    Just bring your own LX-300 with worn out ribbon.

    1. Primus Secundus Tertius

      Re: LX

      There's life yet in my old (30 yrs) Epson dot matrix printer.

      1. Jonathan Richards 1 Silver badge

        Re: LX

        @ I II III

        Hoo, boy, you wouldn't believe how individual the placements of those dots are! Nearly as good as the mis-aligned letters on a typewriter, a forensic clue beloved of spy thrillers of yesteryear.

        Something that the paper itself didn't seem to address in the anonymization-by-adding dots technique, is whether the serial numbers in human-readable form have some sort of error detection/correction, along the lines of check-digits in an ISBN, for example. The serial numbers are many digits long; much too long unless the manufacturers are planning to build billions of printers.

  8. Dante Alighieri

    from little Acorns

    my RISC PC drives just dots...

    and I thinkn the AMSTRAD printers were just dot engines...

    I will remember not to unpack my STAR given the comment above.

    Will the olivetti BJ be susceptible to this?

    It seems that you have to be seriously up the political chain of influence for your print outs to be subjected to this. My Scout program print outs are probably not going to attract the 5 Eyes.

  9. Lee Mulcahy

    In response to many of the previous comments...

    Codes are unique to the printer, not the document. Some include date/time stamps

    Laser printers only (so far)

    Printouts with three-color images (so far)


  10. Brian Miller

    Special algorithm not required

    After their algorithm identifies the pattern in use, it takes a mask of all possible dot locations in that pattern, and adds extra dots that conform to the layout, but render the code meaningless.

    Or you could just use an image filter in the paint program. Really, this is silly. When you know these dots exist, defeating the encoding without special software is trivial, as they note.

  11. Anonymous Coward
    Anonymous Coward

    Trackers are not stupid

    If you can think of a way that you think is going to defeat them, you are deluded. A significant amount of effort goes into these techniques, and just because you think you know about one, that's no indication they're not using others. There are such a huge number of different ways to track documents, with "dots" being the most stupid, it's certain they're doing more than just that - in fact - the dots might be a decoy to make you think you worked out what they're doing, so you don't look more closely at what else they're doing...

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