Seth Schoen gives a good summary of printer dot issues in Printer Tracking Dots Back in the News.
From the post:
Several journalists and experts have recently focused on the fact that a scanned document published by The Intercept contained tiny yellow dots produced by a Xerox DocuColor printer. Those dots allow the document’s origin and date of printing to be ascertained, which could have played a role in the arrest of Reality Leigh Winner, accused of leaking the document. EFF has previously researched this tracking technology at some length; our work on it has helped bring it to public attention, including in a somewhat hilarious video.
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Schoen’s post and references are fine as far as they go, but there are other dangers associated with printers.
For example:
- The material in or omitted from a document can by used to identify the origin of a document.
- The order of material in a document, a list, paragraph or footnote can be used to identify the origin of a document.
- Micro-spacing of characters, invisible to the naked eye, may represent identification patterns.
- Micro-spacing of margins or other white space characteristics may represent identification patterns.
- Changes to the placement of headers, footers, page numbers, may represent identification patterns.
All of these techniques work with black and white printers as well as color printers.
The less security associated with a document and/or the wider its distribution, the less likely you are to encounter such techniques. Maybe.
Even if your source has an ironclad alibi, sharing a leaked document with a government agency is risky business. (full stop)
Just don’t do it!