Tracking Printers to Fight Crime

Q. Is it true that laser printers put an invisible code that contains the printer’s serial number on every document printed?

A. Some, but not all, laser printers do leave a series of nearly imperceptible yellow dots on the printed page. These dots usually contain the encoded serial number of the printer and may also include the time and date that the document was printed.

The so-called yellow tracking dots have been found on more than 100 colour laser printer models from major manufacturers. The dots are used by Secret Service to track counterfeiters. As anyone with a colour laser printer of good quality should know, the ability to print fake money has become much easier but no less illegal.

The Secret Service has said it decodes only the information contained in the dots to investigate counterfeiting cases. Once it has the serial number of the printer, the agency can work with printer companies to find out where the printer was sold.

The existence of these dots has long had privacy advocates worried. The Electronic Frontier Foundation, a privacy rights group, has been closely following the yellow dots issue because there are no legal provisions to stop government agencies from using the technology to track documents in cases unrelated to counterfeiting.

Source: J.D. Biersdorfer, New York Times
Extend reading: Is Your Printer Spying On You?
Electronic Frontier Foundation (EFF):
List of Printers Which Do or Do Not Display Tracking Dots