Do you use a color laser printer in your home or office? If so, it almost certainly adds identifying code to all of your documents telling the date and time a document was printed along with the printer’s serial number. How does it work? In one method, the printers add tiny yellow dots to the document. The yellow ink is low contrast against white paper, making the tiny dots invisible to the naked eye. The yellow dot technology appears to be used only in color laser printers and copiers. Monochrome laser, LED and inkjet printers do not have the yellow toner needed to print the dots so they do not produce these markings.
Although this technology has been used at least since the 1990s, it is likely other types of tracking are also in use now. The Electronic Frontier Foundation says that it is probably safest to assume that all modern color laser printers include some kind of tracking information.
While the stated purpose of this tracking is to identify criminal activity (such as counterfeiting), it can also be used to identify whistleblowers. In 2017, FBI agents arrested Reality Winner, a government contractor who had allegedly leaked a confidential document to the press. It is believed that Winner was identified through a pattern of yellow “microdots” on the leaked documents that revealed the date and time the documents were printed as well as the serial number of the printer.
Can you turn off this feature or do anything to conceal your printer’s information in the documents you print? Printer manufacturers are understandably close-mouthed about how (or even if) their equipment tracks users, so they do not offer any guidance on disabling this feature. However, German researchers have developed a tool that masks or anonymizes the dot pattern to protect users’ identities. Of course, it will probably not work against printers that use other types of tracking systems.
If you are using your printer for illicit activities (or even to expose the illicit activities of others) you should assume that the printer will point law enforcement to you.
