In a case of closing the barn door after the horses are out, federal employees are being warned not to look at documents leaked by WikiLeaks website, noting that despite their wide release, the hundreds of thousands of stolen papers are still classified by the U.S. government.

An internal memo sent late last week from the Office of Management and Budget and obtained by Fox News says that federal employees and contractors are "obligated to protect classified information pursuant to all applicable laws, and to use government information technology systems in accordance with agency procedures so that the integrity of such systems is not compromised."

The memo, which calls the disclosure damaging to national security, must be "declassified by an appropriate U.S. government authority" before it can be viewed by personnel that don't have the security clearance.

WikiLeaks has distributed hundreds of thousands of pages of U.S. classified material from the Pentagon and State Department and claims to have an "insurance" file to release of additional information should any harm come to WikiLeaks founder Julian Assange. The file has been uploaded and ready to go since July, and while U.S. officials aren't sure what's in it, the file has a 256-key encryption that code breakers say may be impossible to crack.

Despite the gravity of the situation, Secretary of State Hillary Clinton is doing her best to make light of the U.S. embarrassment. At a reception she hosted Saturday night at the State Department for recipients of this year's Kennedy Center Honors, who include Oprah Winfrey and Paul McCartney, Clinton said she found it extraordinary to greet so many talented people.

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"I am writing a cable about it, which I'm sure you'll find soon on your closest website," she joked.

While Clinton jokes about the non-classified documents, Senate Republican Leader Mitch McConnell, called Assange "a high-tech terrorist" who "has done enormous damage to our country."

"I think he needs to be prosecuted to the fullest extent of the law. And if that becomes a problem, we need to change the law. I think it's done enormous damage to our country and to our relationships with our allies around the world," McConnell said.

Despite the danger and the rules on reading the documents, federal employees are permitted to read "non-classified, publicly available news reports" that discuss classified material as long as they don't open up attachments that lead to classified papers.

The OMB notice sent Friday "restates and reinforces existing restrictions on access to classified documents by unauthorized personnel or on computers that access the web via non-classified government systems," said OMB spokeswoman Moira Mack.

"It reinforces existing requirements to protect the integrity of non-classified government systems, and to prevent spillage of classified material onto non-classified systems."

The OMB said the guidance does not "advise agencies to block WikiLeaks or other websites on government computer systems."

Those with the appropriate clearance can read the appropriate documents for that clearance.

Fox News' Mike Emanuel and The Associated Press contributed to this report.