Printer makers in 'secret deal' with spooks

Some colour laser printers encode the time, date and serial number of every print-out

Research by the Electronic Frontier Foundation (EFF) has revealed that some colour laser printers encode the time, date and serial number of every print-out in a coded format that can be read by US government agencies.

According to the EFF, the US Secret Service has admitted that it arranged for information to be encoded, but declined to say what information was stored.

The EFF has now decoded the information, which it claims includes the time and date of printing and the serial number of the printer making the image.

"We have found that the dots from at least one line of printers encode the date and time that your document was printed, as well as the serial number of the printer," said EFF staff technologist Seth David Schoen.

"So far, we have only broken the code for Xerox DocuColor printers. But we believe that other models from other manufacturers include the same personally identifiable information in their tracking dots."

A list of which printers use the system is available here. The EFF has also compiled a guide for users to check their own print-outs for the markings. 

The dots, which are printed in yellow toner, are less than a millimetre wide and are repeated across every page printed. They can only be found by examining the paper under blue light.

According to the EFF team the US Secret Service, which is responsible for combating counterfeiting operations as well as protecting the president, said that it only uses the information in criminal prosecutions.

But the EFF has pointed out that such tools could be used to stifle political opposition, and accused the printer manufacturers of making "backroom deals" with the US government.

In order to speed up its investigations the EFF has asked for volunteers to print test sheets for analysis. More details can be found here.