EFF exposed hidden printer tracking dots with a crowdsourced test list

In late 2004, EFF began warning that many color laser printers print nearly invisible yellow dots on every page — a machine identification code that can tie a document to the printer that produced it. Documents the organization obtained through FOIA suggested that major manufacturers had entered a secret agreement with governments to keep that forensic tracing possible, while the people using the printers had no way to know their output was tagged.

EFF's answer was to make the secret measurable. Its research team broke the code behind the dots — by the organization's 2005 account, the U.S. Secret Service admitted the tracking information — and the project recruited volunteers in about a dozen countries, from software firms and symphonies to public schools, physics labs and ice cream parlors, to test printers by printing a page and examining it under blue light or a microscope.

The project published a list of hundreds of color laser models marked yes, no or unclear, each entry backed by who tested it and how, and each "no" hedged: it only meant no yellow dots were visible, not that the printer was clean. Manufacturers were invited to go on record, and the page noted that other forensic marking techniques existed which EFF could not yet detect.

The list became the reference whenever printer tracking resurfaced. A Government Computer News review called HP's tracking codes "a secret spy program"; when The Intercept published a scanned NSA document in June 2017, journalists and experts pointed to the yellow dots produced by a Xerox DocuColor printer; and a warning added to the page that year said it was safest to assume all recent color laser printers encode some forensic code.

Decode the dots and publish a crowdsourced yes/no list, making a covert tracking scheme publicly testable

A printed page and a blue light cost almost nothing, so volunteers worldwide could test far more models than one lab ever could.

A public yes/no list turns rumor into checkable rows: any owner can verify a model, and a wrong entry is refutable.

Publishing the decoding method broke the information monopoly that kept the tracking invisible to the people it tracked.

Honest caveats — "no" does not mean clean — kept the project credible with journalists and experts rather than reading as scaremongering.

Concrete model names gave the press hooks like GCN's "secret spy program" review and the Intercept document, keeping the issue alive for more than a decade.

A secret surveillance capability loses power when you make it checkable: decode the mechanism, crowdsource the testing, and publish an inventory that forces denial or silence to become data.

EFF's list became the canonical answer to "does my printer track me?". EFF filed FOIA requests about agencies' use of the dots and posted nearly 9,000 pages of government documents in a Sunshine Week push. Government Computer News called HP's codes "a secret spy program"; when The Intercept published a scanned NSA document in June 2017, journalists focused on its Xerox DocuColor dots. EFF's closing warning: assume all recent color laser printers print some forensic code, visible or not. The list is no longer updated; its Hacker News discussion drew 586 points and 210 comments in June 2017.