"Air Force One is next," read the message received by the U.S. Secret Service at 9 a.m. Sept. 11, after two hijacked planes struck the twin towers of the World Trade Center in New York.

Three minutes later, Secret Service agents grabbed Vice President Dick Cheney from his seat opposite a television set in the White House and hustled him down to the president's emergency operations center, a bunker built to withstand a nuclear blast.

The terrorists' message threatening Air Force One was transmitted in that day's top-secret White House code words. As the clock ticked away, the Secret Service reached a frightening conclusion: The terrorists had obtained the White House code and a whole set of top-secret signals.

This made it possible for a hostile force to pinpoint the exact position of Air Force One, its destination and its classified procedures. In fact, the hijackers were picking up and deciphering the presidential plane's incoming and outgoing transmissions.

The discovery shocked everyone in the president's emergency operations center ? Cheney, National Security Adviser Condoleezza Rice and Transportation Secretary Norman Mineta. Their first question was: How did the terrorists access top-secret White House codes and procedures? Is there a mole, or more than one enemy spy in the White House, the Secret Service, the FBI, the CIA or the Federal Aviation Administration?

In the week after the attacks in New York and Washington, more hair-raising facts emerged. The terrorists had also obtained the code groups of the National Security Agency and were able to penetrate the NSA's state-of-the-art electronic surveillance systems. Indeed, they seemed to have at their disposal an electronic capability that was more sophisticated than that of the NSA.

This startling observation came as no surprise to those tracking the globe-spanning investments of Saudi Arabia's bin Laden family and those of its exiled son, Osama, in some of the world's biggest and most advanced satellite and telecommunications companies. World Space Communication is one of the known bin Laden assets. U.S. counter-terrorism agencies, including the NSA, have been tracking World Space Communication's activities for the past five years. Some of the company's satellites are far more advanced than the NSA's own eyes in the sky.

Bin Laden also has the NSA beat on the employment front, hiring the best computer experts on the market . One such is Nabil Khan Kani, a Syrian who lived in Barcelona with his Spanish wife, Jenna Florine, in the late 1980s and early 1990s.

No one ever suspected what the amiable Syrian was really up to until January 2000, when FBI agents found two apartments he used thousands of miles from Barcelona, in the Bab el-Shabaa district of Saana, Yemen. The apartments served as transit points for Egyptians suspected of operational links with the Egyptian Islamic Jihad and Algerians connected with the Armed Islamic Group, or GIA. There, investigators turned up nine fake identity cards in different names, all with Kani's photo, Spanish, Italian, French and Sudanese passports, likewise with the same photo but in different names, and two pistols fitted with silencers.

Kani must have used yet another alias for his getaway . His whereabouts are unknown to this day. Computer and terrorism experts suggest that the missing Syrian computer whiz was the author of the technology known as steganography, as first described in the Washington Post yesterday. This technology enables users to bypass electronic monitoring by hiding messages randomly in seemingly innocent digital files, such as music files, those of the popular online marketplace eBay, pornographic files or even e-mail headers. Scrambled with the help of basic encryption tools, they can only be read by those with a "key." These messages leave no trace of their presence.

U.S. intelligence has been unable to trace their authors and recipients in the three years since first detecting evidence of their existence in the files of the bin Laden organization. U.S. agencies now believe that the attacks in New York and Washington were coordinated through those encrypted electronic messages, which were opened by "key" holders.

They also believe that terrorists are in possession of all or part of the codes used by the Drug Enforcement Administration, the National Reconnaissance Office, Air Force Intelligence, Army Intelligence, Naval Intelligence, Marine Corps Intelligence and the intelligence offices of the State Department and Department of Energy.

Intelligence and counter-terror sources report that, while rescuers in New York and Washington were sifting through rubble inch by inch, US government experts were changing codes one-by-one ? and even more difficult, replacing procedures and methods of encryption. The nagging question of a mole in the highest reaches of the U.S. government and intelligence community ? with direct or indirect links with bin Laden ? remains. Since no single individual has access to every top-level code at any given time ? a single mole would not answer the case; it would have to be a large, widely spread number. U.S. experts do not believe bin Laden was capable of infiltrating double agents into the heart of the U.S. administration on a large scale. They are looking elsewhere, instead, at a country with a very well-oiled intelligence apparatus ? Iraq.

This theory was argued by an authoritative voice, former CIA Director James Woolsey, in a New Republic article reprinted by London's Daily Telegraph on Sept. 17. He refers to a book called "Study of Revenge: Saddam Hussein's Unfinished War Against America," by Laurie Mylroie, which quotes a senior FBI investigator on the problematical identity of Ramzi Yousef, perpetrator of the first attempt to blow up the World Trade Center in 1993.

For that deed, a U.S. federal court in New York sentenced Yousef Jan. 8, 1998, to 240 years in solitary confinement. He was also indicted for conspiring to hijack 12 U.S. and Asian commercial aircraft on their way to the United States and blow them up over New York. It was claimed that the name Ramzi Yousef was an alias for his real identity, which was a Pakistani called Abdul Basit Karim.

However, the FBI investigator cited in the book said that Basit was not his real identity either; Yousef was actually an Iraqi army agent who stole Basit's identity. Basit and family were resident in Kuwait when Iraq overran the oil emirate in 1990. The Iraqis moved the family to Baghdad with other hostages. Some returned home, but the Basits were never heard of again, probably murdered for the sake of disguising Ramzi Yousef.

The former CIA director's advice is this: Iraq was involved in the first attack on the World Trade Center. Baghdad is therefore the place to look for the conspirators behind the second.

Intelligence sources can disclose that Woolsey's conclusion does not rest exclusively on the Mylroie book. While pointing the finger at Iraqi intelligence, he assigns Baghdad with no more than a partial role both in the1993 World Trade Center bombing and also in last week's suicide attack on its twin towers. His conclusions are based on a CIA investigation opened during his tenure as CIA director from 1993-1995.

Evidence kept in a personal dossier codenamed KG-84-HJ established Iraqi complicity in the 1993 attack. It also contains the first serious evaluations and theories regarding the identity of the high-placed penetration agents in the White House and at the heart of U.S. intelligence.

They appear to be the very moles who made those vital coded signals available to the kamikaze terrorists on 911. ___

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