EFF’s blog has a post about a new way libraries could accidentally infringe on patron privacy. Some common color laser printers have the ability to encode uniquiely identifying and traceable information into pages they print. If you care enough about patron privacy to not reveal if a patron has a library card, would you care enough to not reveal that they have used your computers/printers?
According to experts, several printer companies quietly encode the serial number and the manufacturing code of their color laser printers and color copiers on every document those machines produce. Governments, including the United States, already use the hidden markings to track counterfeiters.
Peter Crean, a senior research fellow at Xerox, says his company’s laser printers, copiers and multifunction workstations, such as its WorkCentre Pro series, put the “serial number of each machine coded in little yellow dots” in every printout. The millimeter-sized dots appear about every inch on a page, nestled within the printed words and margins.