The Electronic Frontier Foundation (EFF) has apparently uncovered the mystery behind the tiny dots that some color printers have been secretly inserting into printed documents. According to the report by the EFF's Seth Schoen
, the Secret Service has issued the following admission:
The U.S. Secret Service admitted that the tracking information is part of a deal struck with selected color laser printer manufacturers, ostensibly to identify counterfeiters. However, the nature of the private information encoded in each document was not previously known.
According to Schoen, "We've found that the dots from at least one line of printers encode the date and time your document was printed, as well as the serial number of the printer." To give you an idea of how surreptitious the dots are, Schoen's report goes on to say:
The dots are yellow, less than one millimeter in diameter, and are typically repeated over each page of a document. In order to see the pattern, you need a blue light, a magnifying glass, or a microscope (for instructions on how to see the dots, see: http://www.eff.org/Privacy/printers/docucolor/).
The EFF has also published a list of the printers that it has tested so far.