The revelation that users of color laser printers can be tracked through secret codes in documents will alarm conspiracy buffs, but the latest hint of Big Brother ought to concern any American who values the right of privacy.

The U.S. Secret Service confirms that a pattern of tiny yellow dots in at least some color-laser printouts can reveal the date and time the document was produced as well as the serial number of the printer, information the agency uses to fight counterfeiting.

The same tracking data, of course, could lead fairly easily to identify any printer's user -- a whistle-blower, for example -- and abuse of civil liberties by a government so inclined. That's a legitimate concern, especially considering the obsession with secrecy and control on the part of the Bush administration. Also troublesome is the clandestine manner in which the printer industry apparently collaborated with government to put the code in place.

The code, which supposedly can be read only by the Secret Service, was cracked recently by the Electronic Frontier Foundation, a consumer privacy advocate. The telltale yellow dots appear in documents produced on virtually every make of color laser printers, although the organization says it so far has broken the code only for one particular Xerox model.

The Secret Service insists that the code is being used only to fight counterfeiting of U.S. currency, a $40 million a year problem. If that's the case, only counterfeiters need fear detection. But recent history is replete with instances when government spied on individuals who oppose official policy but committed no crime, such as Vietnam War protesters.

As an EFF attorney put it, "Underground democracy movements that produce political or religious pamphlets and fliers, like the Russian samizdat of the 1980s, will always need the anonymity of simple paper documents, but this technology makes it easier for governments to find dissenters. Even worse, it shows how the government and private industry make back-room deals to weaken our privacy by compromising everyday equipment like printers."

We realize that counterfeiting is a serious problem, and that most of today's bogus bills are produced with digital scanners, copiers and printers. But it is also true that the same technology can be turned against the citizens it is supposed to protect.