Little yellow dots may have led to the arrest of Reality Leigh Winner.
Little yellow dots may have led to the arrest of Reality Leigh Winner.

A little known method of tracking a user's identity has been revealed in the case of Reality Leigh Winner, the 25-year-old whistleblower who leaked a classified document to the media from her office at an NSA subcontractor.

The top secret intelligence report Winner sent to The Intercept made its way to the FBI after the news outlet submitted it to the bureau for validation. The FBI was able to determine that the file was a scan of a printed document because agents noticed a crease down its middle. As Winner was only one of six people who might have printed out the doc, and the only one to have contacted The Intercept via email on her work computer, the FBI was able to quickly track her down.

But, a little known, and questionable, surveillance strategy might also have been in play in her arrest.

Perhaps unknown to Winner, every sheet of paper that passes through a color digital printer is stamped with a code: tiny yellow dots in which are embedded the serial number of the color printer, as well as the date and time the document was printed.

Although the affadavit submitted by the FBI did not mention the use of this method, when Winner printed out the top-secret intelligence report detailing Russian meddling in the American election, an analysis by trained investigators could have detected the digital stamp.

The Electronic Frontier Foundation released a statement in which it explained how the tracking technology has been in use for at least a decade – the result of what it called secret agreements between a number of governments and the printer vendors

While some printer manufacturers acknowledge that their devices carry the tracking mechanism, they offer few details, the EFF said. And, while the original impetus for creating the technology was to impede the counterfeiting of currency, there's little to stop the technique from being applied to other purposes, said the statement. 

"Overall, this secret nonconsensual tracking makes it more difficult to publish any kind of document anonymously, which implicates both privacy and speech."

The technology is another example, the EFF said, of how the government pressures industry in ways which undermine privacy. "We should insist that companies be transparent about how government requests have affected the design of the products we use, since those designs can have profound implications."