Is your printer going to turn you in?

A twitter posting from Andy Carvin alerted me to this unnerving situation. According to Threat Level, a blog on security and privacy issues at Wired magazine, Manufacturers of color laser printers quietly cooperated with the Secret Service to print nearly invisible tracking codes on every color page printed through laser printers individuals buy, ostensibly as a way to track down forgeries. According to a page maintained by the MIT Media Lab, a pattern of nearly undetectable yellow dots is printed on each page: 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). The Electronic Freedom Foundation (EFF) has posted a list of the printers and manufacturers known to support this surreptitious tracking.