Defense Secretary Donald Rumsfeld warned in a directive sent to military units this week that too much unclassified but worrisome material was popping up on the Web, and said Al Qaeda and other foes were sure to take advantage of it.

The directive, drafted as the U.S. is readying troops for a possible attack on Iraq, reminded military Webmasters they must adhere to the department's 1998 policies and procedures.

Rumsfeld's order further restricts what information will be publicly available on military sites, effectively tightening controls that have been in place for at least five years and that became far more strict after the terrorist attacks on the World Trade Center and the Pentagon.

"An Al Qaeda training manual recovered in Afghanistan states: 'Using public sources openly and without resorting to illegal means, it is possible to gather at least 80 percent of information about the enemy,'" Rumsfeld wrote. "At more than 700 gigabytes, the DoD Web-based data makes a vast, readily available source of information on DoD plans, programs and activities. One must conclude our enemies access DoD Web sites on a regular basis."

Steven Aftergood, an analyst at the Federation of American Scientists who works to limit government secrecy, says that Rumsfeld's order is too broad.

"I'm concerned that it sends a chilling signal that will only accelerate the withdrawal of public information from the Web," Aftergood said. "If he had said anything like operational plans should not be on the Web, I'd be hard pressed to disagree with that. But what he said is that anything that might be useful to an adversary should not be on the Web. And that is overreaching, because anything could be useful to an adversary."

The Federation of American Scientists, which was founded in 1945 by Manhattan Project scientists, removed hundreds of documents from its vast archive of military information after the Sept. 11 attacks. But Aftergood said the information included photos of military bases and building schematics that represented only a small fraction of the total the group makes available to the public.

There have been no confirmed reports about classified information making its way to military sites, but Rumsfeld said he was concerned about other categories he dubbed "sensitive" or "for official use only." Rumsfeld's directive was first reported by InsideDefense.com.

Rumsfeld said that 1,500 instances of such public distribution have been spotted in the last year. Those appearances could violate the 1998 DoD policy, which says: "A DoD Web site may not post For Official Use Only information, or information not specifically cleared and approved for public release unless it employs adequate security and access controls."

Since the Sept. 11 attacks, the Bush administration has "vastly expanded the zone of secrecy that surrounds the White House and most of the federal government," according to an October 2002 report from the advocacy group OMB Watch. The report says that thousands of documents and tremendous amounts of data have been removed from government sites, including airport safety data, environmental data, and information that remains available on private-sector sites.

In an October 2001 memorandum distributed throughout the government, Attorney General John Ashcroft formally reduced the amount of information federal agencies would make available. Ashcroft wrote that in nearly all cases, the Justice Department would seek to defend an agency's decision not to release records requested under the Freedom of Information Act.