"After his capture he admitted being an al Qaeda member and agreed to send e-mails to his contacts," a Pakistani intelligence source told Reuters. "He sent encoded e-mails and received encoded replies. He's a great hacker and even the U.S. agents said he was a computer whiz."

Khan was the source for reports that al-Qaida was planning attacks on financial institutions in New York, Newark and Washington, D.C., spurring Homeland Security Director Tom Ridge to raise the national alert status to orange last Sunday.

But the undercover operative's value as a critical intelligence asset went up in smoke on Monday when the New York Times named the previously unidentified Khan, calling him "a kind of clearinghouse of Qaida communications" and "a vital source of information" on terrorist operations.

Once Khan was outed, British authorities scrambled to round up al-Qaida suspects he had identified before they were able to go underground.

"By exposing the only deep mole we've ever had within al-Qaida, it ruined the chance to capture dozens if not hundreds more," former Justice Department prosecutor John Loftus told Fox News on Saturday.

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