The recent arrest of Reality Winner, the 25-year-old NSA contractor accused of leaking classified documents on Russian efforts to hack U.S. voting systems, has brought light to tracking embedded in paper printouts. Security professionals believe that Winner was caught due to tiny yellow dots printed on the documents–and on every piece of paper that goes through particular printers. These dots, which can be revealed by shining a blue light or by digital magnification, typically include the date/time of the printout and a printer serial number. It is speculated that the information revealed from the yellow dots was used to tie Winner’s work printer history to the documents. EFF has previously decoded the yellow dots for some printers, and has created a guide.
One argument for the inclusion of the tracking dots is to prevent counterfeiting, such as attempts to print money. EFF writes that printed page tracking is a result of the government asking printer companies to include it without the law’s requirement and that it represents a lack of transparency.