The Stack Archive

Secret tracking code in colour printers enables government spying

Mon 19 Oct 2015

Woman using printer

A research team at the Electronic Frontier Foundation (EFF) has broken the code found behind tracking dots hidden in documents produced by some colour laser printers.

The U.S. Secret Service has admitted that the printed code was part of a deal with laser printer manufacturers to help identify counterfeited documents. However, until recently the type of information stored has been unknown.

“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,” said EFF technologist Seth David Schoen.

The coded dots were found on documents printed by machines from Xerox, Canon, Brother, Dell and HP. The dots are yellow and measure less than a millimetre in diameter. The pattern is typically repeated on each page of a document, and is only recognisable under blue light, a magnifying glass, or a microscope.

Screen Shot 2015-10-19 at 15.19.59The EFF researchers have thus far only broken the code for Xerox DocuColor printers, but they believe that other printer models and brands could include the same personally identifiable information.

The Secret Service maintains that the information found in the tracking dots is only used in criminal counterfeit investigations. However, as the EFF contends, there is no legislation to prevent governments from ‘abusing’ the information.

“Underground democracy movements that produce political or religious pamphlets and flyers, like the Russian samizdat of the 1980s, will always need the anonymity of simple paper documents, but this technology makes it easier for governments to find dissenters,” added EFF senior staff attorney Lee Tien.

“Even worse, it shows how the government and private industry make backroom deals to weaken our privacy by compromising everyday equipment like printers. The logical next question is: what other deals have been or are being made to ensure that our technology rats on us?” he continued.


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