Bush's America Indeed

'Most color laser printers made and sold today intentionally add invisible information to make it easier to determine where (and when) a particular document was printed.

This seems to have been done as part of a secret deal between the United States Secret Service and the individual manufacturers.

Some of the manufacturers have mentioned the existence of the tracking information in their documentation, and others haven't.

None of them have explained exactly how it works or what information is conveyed.

No law requires printer companies to help track printer users this way, and no law prevents them from stopping this practice or giving customers a solution to avoid being tracked.

This information is most famously known to be coded by patterns of yellow dots that the printers add to the background of all the pages they print.

The yellow dots are hard to see with the naked eye, but can be seen under bright blue light or with a microscope.

Their arrangement reveals which printer was used to print a particular document, and sometimes also shows when it was printed.

Some of the codes have been understood while others are still mysterious, but none of the printer manufacturers has denied that the dots are intended to help track a particular document to a particular printer (or that they can actually be used for this purpose).

This is a direct attack on the privacy of the owners and users of printers, and in particular, on their right to free, anonymous speech.'

Is Your Printer Spying On You?

And yikes:

'This goes way beyond ID - most color printers/copiers (and more recent versions of Photoshop) are coded to auto-detect images of currency and do Bad Things when it does.

I ran into this first hand about ten years ago at a job where I was printing internal "Certificates" to a color copier. The copier interpreted the filigreee border as counterfeit currency, and printed black squares over it for the first few copies, then shut down completely.

The copier repair guy was called out, who told me that apparently, not only does it "black out" what it thinks is currency, but the algorithm becomes more sensitive each time it gets triggered (to prevent experimentation) and locks up after enough "attempts" requiring an auth code from the manufacturer to unlock. I also had to give the repairman copies of what we were trying to print, and was told that the manufacturer would send them, along with an incident report, to the Secret Service "for their records".'