DP's Security Bits

Color laser printers sure are nifty, but they might be a little more nifty than you bargained for because certain printers made by manufacturers such as Canon, Epson, HP, Lexmark, Xerox, and others place tracking dots on every document you print. Why are they there? Ask the U.S. Secret Service.

Manufacturers place the dots on printed documents as part of a deal with the Secret Service, which the EFF (Electronic Frontier Foundation) says is ostensibly to catch counterfeiters. Although this practice hasn’t always been a secret, the information that’s placed on the documents was unknown until the EFF recently conducted research to break the code that’s used in at least one of the printers.

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, says EFF Staff Technologist Seth David Schoen.

According to the EFF, you won’t even notice the dots unless you look at a printed page with a blue light and a magnifying glass or microscope. The yellow dots are less than 1 millimeter in diameter and usually repeat over each page of a document.

It shows how the government and private industry make backroom deals to weaken our privacy by compromising everyday equipment like printers, says EFF Senior Staff Attorney Lee Tien.