Eric Lipton

In a classic case of shutting the barn door after the horse has left, the Obama administration and the Department of Defense have ordered the hundreds of thousands of federal employees and contractors not to view the secret cables and other classified documents published by Wikileaks and news organizations around the world unless the workers have the required security clearance or authorization.

“Classified information, whether or not already posted on public websites or disclosed to the media, remains classified, and must be treated as such by federal employees and contractors, until it is declassified by an appropriate U.S. Government authority,” said the notice sent on Friday afternoon by the Office of Management and Budget, which is part of the White House, to agency and department heads, urging them to distribute it to their staff.

The directive applies to both government computers and private devices that employees or contractors might have, as long as they are accessing the documents on nonclassified government networks. It does not advise agencies to block WikiLeaks or other websites on government computer systems, a White House official said Saturday. And it does not prohibit federal employees from reading news stories about the topic. But if they have accidentally already downloaded any of these documents, they are being told to notify their “information security offices.”

The Department of Defense, in its own directive to military personnel and contractors, says that simply viewing these documents, without proper authorization, will violate long-standing rules even though they are accessible to the public at large on Internet sites.

"Viewing or downloading still classified documents from unclassified government computers creates a security violation," a spokeswoman said in a statement on Saturday.

The effort, while understandable, seems entirely futile, said Marc Rotenberg, executive director of the Electronic Privacy Information Center, a Washington nonprofit group that has combated government efforts to keep certain government documents secret.

“It just may be a little too late for the government to push these documents down the memory hole,” Mr. Rotenberg said, adding that his center did not support the initial public release of the material. “This is Orwell thought police in the age of the Internet, as these are already so widely accessible on servers around the world.” The Library of Congress has joined in the push, blocked visitors to its reading rooms, or anyone else using its computer system, from accessing the WikiLeaks site, noting that “unauthorized disclosures of classified documents do not alter the documents’ classified status or automatically result in declassification of the documents.”

The moves have not apparently discouraged staff at WikiLeaks, as the organization continues to post Twitter feeds mocking the efforts to limit access to the documents, including one note on Saturday reading: “Digital McCarthyism: U.S. Military Tries to Intimidate Soldiers Into Not Reading Wikileaks”.