Computer experts called 2003 ''the Year of the Worm.'' For 12 months, digital infections swarmed across the Internet with the intensity of a biblical plague. It began in January, when the Slammer worm infected nearly 75,000 servers in 10 minutes, clogging Bank of America's A.T.M. network and causing sporadic flight delays. In the summer, the Blaster worm struck, spreading by exploiting a flaw in Windows; it carried taunting messages directed at Bill Gates, infected hundreds of thousands of computers and tried to use them to bombard a Microsoft Web site with data. Then in August, a worm called Sobig.F exploded with even more force, spreading via e-mail that it generated by stealing addresses from victims' computers. It propagated so rapidly that at one point, one out of every 17 e-mail messages traveling through the Internet was a copy of Sobig.F. The computer-security firm mi2g estimated that the worldwide cost of these attacks in 2003, including clean-up and lost productivity, was at least $82 billion (though such estimates have been criticized for being inflated).
The pace of contagion seems to be escalating. When the Mydoom.A e-mail virus struck in late January, it spread even faster than Sobig.F; at its peak, experts estimated, one out of every five e-mail messages was a copy of Mydoom.A. It also carried a nasty payload: it reprogrammed victim computers to attack the Web site of SCO, a software firm vilified by geeks in the ''open source'' software community.
You might assume that the blame -- and the legal repercussions -- for the destruction would land directly at the feet of people like Mario. But as the police around the globe have cracked down on cybercrime in the past few years, virus writers have become more cautious, or at least more crafty. These days, many elite writers do not spread their works at all. Instead, they ''publish'' them, posting their code on Web sites, often with detailed descriptions of how the program works. Essentially, they leave their viruses lying around for anyone to use.
Invariably, someone does. The people who release the viruses are often anonymous mischief-makers, or ''script kiddies.'' That's a derisive term for aspiring young hackers, usually teenagers or curious college students, who don't yet have the skill to program computers but like to pretend they do. They download the viruses, claim to have written them themselves and then set them free in an attempt to assume the role of a fearsome digital menace. Script kiddies often have only a dim idea of how the code works and little concern for how a digital plague can rage out of control.
