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Color laser printers from Canon, Epson, HP, Lexmark, Xerox and others are placing tracking dots on your documents. Dots are placed on printed documents as part of a deal with the Secret Service, which the EFF (Electronic Frontier Foundation) says is to "catch counterfeiters." The date/time of document printing was encoded on the dot, as well as the serial number of the printer. You won't be able to see the dots without a blue light and a magnifying glass. Yellow dots.