IT IS JAN. 17, 2001, the 10th anniversary of the U.S. bombing campaign against Baghdad, Iraq.
Suddenly, an hour after the opening bell, the computers at the New York Stock Exchange flicker off. A jumbo jet landing at Chicago's O'Hare airport crashes when a bogus tower message tells it to land on a crowded runway. On board the USS Eisenhower in the Persian Gulf, angry sailors demand to know why their bank accounts back home have been emptied.
For the first time in the history of warfare, the American mainland has been invaded - but not by troops. A hostile nation has attacked with the silent and invisible weapons of cyberspace.
The Pentagon strategists who once pondered the effects of a Soviet nuclear strike now are studying such a scenario: How real is the threat? Where does it come from? As it builds America's defense against the new threat from "information warfare," the Pentagon has turned to its electronic brain trust: the National Security Agency.
Still reorganizing after the demise of its Cold War mission - and showing the keen survival instincts of any government bureaucracy - NSA has been eager to oblige. At a gathering of intelligence officers in June, the agency's director, Vice Adm. John M. "Mike" McConnell, sounded the alarm.
"We're more vulnerable than any nation on earth," he said. "The things that are vulnerable are U.S. banks, global finance, the stock market, the Federal Reserve, air traffic control, all those things."
NSA's efforts to seize the lead on information warfare is only one of its moves since the end of the Cold War to preserve its paramount role in intelligence. Even as it has slashed coverage of the former Soviet Union and cut personnel by 10 percent in three years, NSA has shifted resources to make itself useful to U.S. policy-makers. The agency has:
* Scrambled to retrain hundreds of Russian linguists to keep pace with shifting crises in other countries.
* Moved swiftly to expand coverage of negotiations by foreign trade officials, bribery attempts by foreign businesses competing with U.S. companies and money transfers by
* Ended its long reluctance to become involved in the war on drugs by working closely with the Drug Enforcement Administration and the FBI on dismantling South American cocaine cartels.
* Increased its role in tracking terrorists and their financial backers, especially since the 1993 bombing of the World Trade Center in New York.
* Used its supercomputing ability to sift millions of transactions for evidence of rogue nations purchasing nuclear, biological and chemical weapons components.
A 21st-century war
Nothing better illustrates NSA's dramatic break with its Cold War past than the agency's move into information warfare.
In an era of shrinking budgets, the threat of terrorist hackers wielding software weapons with such names as worms, Trojan horses, logic bombs, packet sniffers and malicious code may be sufficiently alarming to conjure money from a deficit-minded Congress.
The new field is a boon for NSA's information security experts who traditionally have labored on mundane tasks while the eavesdroppers captured the glory. Now NSA's "INFOSEC" specialists are sought after by worried managers throughout the federal government and corporate America.
By building a computerized society, the United States has left itself wide open to electronic attack. From bank machine networks and the telephone system to electric power companies and steel manufacturers, the U.S. economy is supported by a web of computers.
Admiral McConnell acknowledges it's difficult to persuade the public and Congress to spend hundreds of millions of dollars on a threat that sounds like science fiction.
Yet the first shots already have been fired in this 21st-century war.
In August, a computer hacker in St. Petersburg, Russia, stole $400,000 from Citibank. Earlier this year, a British teen-ager used his personal computer to break into sensitive U.S. Air Force files on North Korean nuclear inspections.
In 1993, critical Defense Department computer systems were penetrated by outsiders 134 times. Last year the number was 256. This year it may approach 500, according to Pentagon officials, who believe that hundreds more intrusions go undetected.
Such intrusions lead some experts to fear a far more devastating surprise attack, the electronic equivalent of Pearl Harbor. Neither America's nuclear missiles nor formidable armed forces can protect it from a malevolent foe with a computer and modem.
Fiction has recently discovered the dramatic possibilities. The new James Bond movie, "Goldeneye," revolves around a villain's electronic attack on England. Author Tom Clancy's latest thriller, "Debt of Honor," tells of Japan taking down U.S. financial markets.
While NSA for decades has worked to make America's most classified computer systems tamperproof, it has spent the last several years focusing on the vulnerable Pentagon systems containing such sensitive information as medical records and supplies.