For years there have been rumors of strange markings on Xerox printer documents and hidden messages that only Xerox is able to decode. Well now the EFF (Electronic Frontier Foundation) has broken the Xerox code and proven that there is in fact forensic evidence on each Xerox printed document. Here’s a brief synopsis from the EFF.
EFF: Because of their limited contrast with the background, the forensic dots are not usually visible to the naked eye under white light. They can be made visible by magnification (using a magnifying glass or microscope), or by illuminating the page with blue instead of white light. Pure blue light causes the yellow dots to appear black. It can be helpful to use magnification together with illumination under blue light, although most individuals with good vision will be able to see the dots distinctly using either technique by itself.