Mario stubs out his cigarette and sits down at the desk in his bedroom. He pops into his laptop the CD of Iron Maiden's Number of the Beast, his latest favourite album. 'I really like it,' he says. 'My girlfriend bought it for me.' He gestures to the 15-year-old girl with straight dark hair lounging on his bed and she throws back a shy smile. Mario, 16, is a secondary-school student in a small town in the foothills of southern Austria. (He didn't want me to use his last name.) His shiny shoulder-length hair covers half his face and his sleepy green eyes, making him look like a very young, languid Mick Jagger. On his wall, he has an enormous poster of Anna Kournikova which, he admits sheepishly, his girlfriend is not thrilled about. Downstairs, his mother is cleaning up after dinner. She isn't thrilled these days, either. But what bothers her isn't Mario's poster. It's his hobby.
When Mario is bored, he likes to sit at his laptop and create computer viruses and worms. Online, he goes by the name Second Part to Hell, and he has written more than 150 examples of what computer experts call 'malware': tiny programs that exist solely to self-replicate, infecting computers hooked up to the internet. Sometimes, these programs cause damage and sometimes they don't. Mario says he prefers to create viruses that don't intentionally wreck data, because simple destruction is too easy. 'Anyone can rewrite a hard drive with one or two lines of code,' he says. 'It makes no sense. It's really lame.' Besides which, it's mean, he says, and he likes to be friendly.

But still - just to see if he could do it - a year ago he created a rather dangerous tool: a program that autogenerates viruses. It's called a Batch Trojan Generator and anyone can download it freely from Mario's website. With a few simple mouse clicks, you can use the tool to create your own malicious 'Trojan horse'. Like its ancient namesake, a Trojan virus arrives in someone's e-mail looking like a gift, a jpeg picture or a video, for example, but actually bearing dangerous cargo.

Mario starts up the tool to show me how it works. A little box appears on his laptop screen, politely asking me to name my Trojan. I call it the 'Clive' virus. Then it asks me what I'd like the virus to do. Shall the Trojan horse format drive C:? Yes, I click. Shall the Trojan horse overwrite every file? Yes. It asks me if I'd like to have the virus activate the next time the computer is restarted and I say yes again.

Then it's done. The generator spits out the virus on to Mario's hard drive, a tiny 3k file. Mario's generator also displays a stern notice warning that spreading your creation is illegal. The generator, he says, is just for educational purposes, a way to help curious programmers learn how Trojans work.

But, I could ignore that advice. I could give this virus an enticing name, like 'britney-spears-wedding-clip. mpeg' to fool people into thinking it's a video. If I were to email it to a victim and if he clicked on it and didn't have up-to-date anti-virus software, then disaster would strike his computer. The virus would activate. It would quietly reach into the victim's Microsoft Windows operating system and insert new commands telling the computer to erase its own hard drive.

The next time the victim started up his computer, the machine would find those new commands, assume they were part of the normal Windows operating system and guilelessly follow them. Everything on his hard drive would vanish - emails, pictures, documents, games. Mario drags the virus over to the trash bin on his computer's desktop and discards it. 'I don't think we should touch that,' he says hastily.

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 cashpoint networks 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 website with data.

Then in August, a worm called Sobig.F exploded with even more force, spreading via email that it generated by stealing addresses from victims' computers. It propagated so rapidly that at one point, one out of every 17 email messages travelling 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 criticised for being inflated).

The pace of contagion seems to be escalating. When the Mydoom.A email virus struck in late January, it spread even faster than Sobig.F; at its peak, experts estimated, one out of every five email messages was a copy of Mydoom.A. It also carried a nasty payload: it reprogrammed victim computers to attack the website 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 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. Our modern virus epidemic is thus born of a symbiotic relationship between the people smart enough to write a virus and the people dumb enough - or malicious enough - to spread it.

This development worries security experts, because it means that virus writing is no longer exclusively a high-skill profession. By so freely sharing their work, the elite virus writers have made it easy for almost anyone to wreak havoc online. When the damage occurs, as it inevitably does, the original authors just shrug. We may have created the monster, they'll say, but we didn't set it loose. This dodge infuriates security professionals and the police, who say it is legally precise but morally corrupt. Like a collection of young Dr. Frankensteins, the virus writers are increasingly creating forces they cannot control and for which they explicitly refuse to take responsibility.

'Where's the beer?' Philet0ast3r wondered. An hour earlier, he had dispatched three friends to pick up another case, but they were nowhere in sight. He looked out over the controlled chaos of his one-bedroom apartment in small-town Bavaria. (Most of the virus writers I visited live in Europe; there have been very few active in the United States since 9/11, because of fears of prosecution.) Philet0ast3r's party was crammed with 20 friends who were blasting out punk band Deftones, playing cards, smoking furiously and arguing about politics. It was a Saturday night. Philet0ast3r, a 21-year-old with a small silver hoop piercing his lower lip, wears his brown hair in thick dreads. (Philet0ast3r is an online handle; he didn't want me to use his name.)

His friends finally arrived with a fresh case of beer and his blue eyes lit up. He flicked open a bottle using the edge of his cigarette lighter and toasted the others. A tall blond friend in a jacket festooned with anti-Nike logos put his arm around Philet0ast3r and beamed.

'This guy,' he proclaimed, 'is the best at Visual Basic.'

In the virus underground, that's love. Visual Basic is a computer language popular among malware authors for its simplicity; Philet0ast3r has used it to create several of the two dozen viruses he's written. From this tiny tourist town, he works as an assistant in a home for the mentally disabled and in his spare time runs an international virus-writers' group called the 'Ready Rangers Liberation Front'. I met him, like everyone profiled in this article, online, first emailing him, then chatting in an internet relay chat channel where virus writers meet and trade tips and war stories.

Philet0ast3r got interested in malware the same way most virus authors do: his own computer was hit by a virus. He wanted to know how it worked and began hunting down virus-writers' websites. He discovered years' worth of viruses online, all easily downloadable, as well as primers full of coding tricks. He spent long evenings hanging out in online chat rooms, asking questions, and soon began writing his own worms.

One might assume Philet0ast3r would favour destructive viruses, given the fact that his apartment is decorated top to bottom with anti-corporate stickers. But his viruses, like those of many malware writers, are often surprisingly mild things carrying goofy payloads. One he is developing will install two artificial intelligence chat-agents on your computer; they appear in a pop-up window, talking to each other nervously about whether your antivirus software is going to catch and delete them. Philet0ast3r said he was also working on something sneakier - a 'keylogger'. It's a Trojan virus that monitors every keystroke its victim types, including passwords and confidential email messages, then secretly mails out copies to whoever planted the virus. Anyone who spreads this Trojan would be able to quic

 

kly harvest huge amounts of sensitive personal information.
Technically, 'viruses' and 'worms' are slightly different things. When a virus arrives on your computer, it disguises itself. It might look like an OutKast song ('hey_ya.mp3'), but if you look more closely, you'll see it has an unusual suffix, like 'hey_ya.mp3.exe'. That's because it isn't an MP3 file at all. It's a tiny program and when you click on it, it will reprogram parts of your computer to do something new, like display a message. A virus cannot kick-start itself; a human needs to be fooled into clicking on it. This turns virus writers into armchair psychologists, hunting for new tricks to dupe someone into activating a virus. ('All virus-spreading,' one virus writer said caustically, 'is based on the idiotic behaviour of the users.')

Worms, in contrast, usually do not require any human intervention to spread. That means they can travel at the breakneck pace of computers themselves. A worm's danger lies in its speed: when it multiplies, it often generates enough traffic to crash internet servers. The most popular worms today are 'mass mailers' which attack a victim's computer, swipe the addresses out of Microsoft Outlook (the world's most common email program) and send a copy of the worm to everyone in the victim's address book. These days, the distinction between worm and virus is breaking down. A worm will carry a virus with it, dropping it on to the victim's hard drive to do its work, then emailing itself off to a new target.

The most ferocious threats today are 'network worms', which exploit a particular flaw in a software product (often one by Microsoft). The author of Slammer, for example, noticed a flaw in Microsoft's SQL Server, an online database commonly used by businesses and governments. The Slammer worm would find an unprotected SQL server, then would fire bursts of information at it, flooding the server's data 'buffer', like a cup filled to the brim with water.

Once its buffer was full, the server could be tricked into sending out thousands of new copies of the worm to other servers. Normally, a server should not allow an outside agent to control it that way, but Microsoft had neglected to defend against such an attack. Using that flaw, Slammer flooded the net with 55 million blasts of data per second and in only 10 minutes colonised almost all vulnerable machines.

Computer-science experts have a phrase for this type of fast-spreading epidemic, 'a Warhol worm' in honour of Andy Warhol's prediction that everyone would be famous for 15 minutes. 'In computer terms, 15 minutes is a really long time,' says Nicholas Weaver, a researcher at the International Computer Science Institute in Berkeley, who coined the Warhol term. 'The worm moves faster than humans can respond.' He suspects that even more damaging worms are on the way. All a worm writer needs to do is find a significant new flaw in a Microsoft product, then write some code that exploits it. Even Microsoft admits that there are flaws the company doesn't yet know about.

Virus writers are especially hostile toward Microsoft, the perennial whipping boy of the geek world. From their (somewhat self-serving) point of view, Microsoft is to blame for the worm epidemic, because the company frequently leaves flaws in its products that allow malware to spread. Microsoft markets its products to less expert computer users, cultivating the sort of gullible victims who click on disguised virus attachments.

But it is Microsoft's success that really makes it such an attractive target: since more than 90 per cent of desktop computers run Windows, worm writers target Microsoft in order to hit the largest possible number of victims. (By relying so exclusively on Microsoft products, virus authors say, we have created a digital monoculture, a dangerous thinning of the internet's gene pool.) Microsoft is now so angry that it has launched a counterattack. Last autumn, it set up a $5 million fund to pay for information leading to the capture of writers who target Windows machines. So far, it has announced $250,000 bounties for the creators of Blaster, Sobig.F and Mydoom.B.

The motivations of the top virus writers can often seem paradoxical. They spend hours dreaming up new strategies to infect computers, then hours more bringing them to reality. Yet when they're done, most of them say they have little interest in turning their creations free. Though Philet0ast3r is proud of his keylogger, he said he does not intend to release it into the wild. His reason is partly one of self-protection; he wouldn't want the police to trace it back to him. But he also said he does not ethically believe in damaging someone else's computer.

So why write a worm, if you're not going to spread it?

For the sheer challenge, Philet0ast3r replied, the fun of producing something 'really cool'. For the top worm writers, the goal is to make something that's brand new. A truly innovative worm, Philet0ast3r said, 'is like art'. To allow his malware to travel swiftly online, the virus writer must keep its code short and efficient. 'One condition of art,' he noted, 'is doing good things with less.'

For a virus author, a successful worm brings the sort of fame that a daring graffiti artist used to produce: the author's name automatically replicating itself in cyberspace. When anti- virus companies post on their websites a new 'alert' warning of a fresh menace, the thrill for the author is like getting a great book review: something to crow about and email around to your friends. Writing malware, as one author emailed me, is like creating artificial life. A virus, he wrote, is 'a humble little creature with only the intention to avoid extinction and survive'.

Quite apart from the intellectual fun of programming, though, the virus scene is attractive partly because it's very social. When Philet0ast3r drops by a virus-writers' chat channel late at night after work, the conversation is as likely to be about music, politics or girls as the latest in worm technology. Very occasionally, malware authors even meet for a party; when I visited Mario, we met another Austrian virus writer and discussed code for hours at a bar.

The virus community attracts a lot of smart but alienated young men, libertarian types who are often flummoxed by the social nuances of life. While the virus scene isn't dominated by those characters, it certainly has its share and they are often the ones with a genuine chip on their shoulder.

'I am a social reject,' admitted Vorgon, as he called himself, a virus writer in Toronto with whom I exchanged messages one night in an online chat channel. He studied computer science in college but couldn't find a computer job after sending out 400 CVs. With 'no friends, not much family' and no girlfriend for years, he became depressed. He attempted suicide, he said, by walking out one freezing winter night into a nearby forest for five hours with no jacket on. But then he got into the virus-writing scene and found a community.

'I met a lot of cool people who were interested in what I did,' he wrote. 'They made me feel good again.' He called his first virus FirstBorn to celebrate his new identity. Later, he saw that one of his worms had been written up as an alert on an anti-virus site and it thrilled him. 'Kinda like when I got my first girlfriend,' he wrote. 'I was god for a couple days.'

Vorgon is still angry about life. His next worm, he wrote, will try to specifically target the people who wouldn't hire him. It will have a 'spidering' engine that crawls web-page links, trying to find likely email addresses for human-resource managers, 'like careers@microsoft.com, for example'. Then it will send them a fake CV infected with the worm. (He hasn't yet decided on a payload and he hasn't ruled out a destructive one.) 'This is a revenge worm,' he explained, 'for not hiring me, and hiring some loser who is not even half the programmer I am.'

Many people might wonder why virus writers aren't rounded up and arrested for producing their creations. But in most countries, writing viruses is not illegal. Indeed, in America some legal scholars argue that it is protected as free speech. Software is a type of language and writing a program is akin to writing a recipe. It is merely a bunch of instructions for the computer to follow, in the same way that a recipe is a set of instructions for a cook to follow.

A virus or worm becomes illegal only when it is activated, when someone sends it to a victim and starts it spreading in the wild, and it does measurable damage to computer systems. The top malware authors are acutely aware of this distinction. Most virus-writer websites include a disclaimer stating that they exist purely for educational purposes, and that if a visitor downloads a virus to spread, the responsibility is entirely the visitor's.

One of the youngest virus writers I visited was Stephen Mathieson, a 16-year-old in Detroit whose screen name is Kefi. He also belongs to Philet0ast3r's Ready Rangers Liberation Front. A year ago, Mathieson became annoyed when he found members of another virus-writers group called Catfish-VX plagiarising his code. So he wrote Evion, a worm specifically designed to taunt the Catfish guys. He put it up on his website for everyone to see. Like most of Mathieson's work, the worm had no destructive intent. It merely popped up a few cocky messages, including Catfish-VX are lamers. This virus was constructed for them to steal. Someone did steal it, because pretty soon Mathieson heard reports of it being spotted in the wild. To this day, he does not know who circulated Evion, but he suspects it was probably a random troublemaker, a script kiddie who swiped it from his site. 'The kids,' he said, shaking his head, 'just cut and paste.'

Quite aside from the strangeness of listening to a 16-year-old complain