[Jason Dookeran] reminded us of something we don’t like to think about. Your printer probably adds barely noticeable dots to everything you print. It does it on purpose, so that if you print something naughty, the good guys can figure out what printer it came from. This is the machine identification code and it has been around since the days that the US government feared that color copiers would allow wholesale counterfiting.
The technology dates back to Xerox and Canon devices from the mid-80s, but it was only publicly acknowledged in 2004. With color printers, the MIC — machine identification code — is a series of tiny yellow dots. Typically, each dock is about 10 microns across and spaced about a millimeter from each other. The pattern prints all over the page so that even a fragment of, say, a ransom note can be identified.
