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 about 'the kids', Mathieson's rhetoric glosses over a charged ethical and legal debate. It is tempting to wonder if the leading malware authors are lying, whether they do in fact circulate their worms on the sly, obsessed with a desire to see if they really work. While security officials say that may occasionally happen, they also say the top virus writers are quite likely telling the truth.

'If you're writing important virus code, you're probably well trained,' says David Perry, global director of education for Trend Micro, an anti-virus company. 'You know a number of tricks to write good code, but you don't want to go to prison. You have an income and stuff. It takes someone unaware of the consequences to release a virus.'

But worm authors are hardly absolved of blame. By putting their code freely on the web, virus writers essentially dangle temptation in front of every disgruntled teenager who goes online looking for a way to rebel. A cynic might say that malware authors rely on clueless script kiddies the same way that a drug dealer uses 13-year-olds to carry illegal goods, passing the liability off to a hapless mule.

Some academics have pondered whether virus authors could be charged under conspiracy laws. Creating a virus, they theorise, might be considered a form of abetting a crime by providing materials. Ken Dunham, the head of 'malicious code intelligence' for iDefense, a computer security company, notes that there are certainly many examples of virus authors assisting newcomers. He has been in chat- rooms, he says, 'where I can see people saying, "How can I find vulnerable hosts?"And another guy says, "Oh, go here, you can use this tool." They're helping each other out'.

There are virus writers who appreciate these complexities, but they are certain that the viruses they write count as protected speech. They insist they have a right to explore their interests. Indeed, a number of them say they are making the world a better place, because they openly expose the weaknesses of computer systems. When Philet0ast3r or Mario or Mathieson finishes a new virus, they say, they will immediately email a copy of it to anti-virus companies. That way, they explained, the companies can program their software to recognise and delete the virus should some script kiddie ever release it into the wild. This is further proof that they mean no harm with their hobby, as Mathieson pointed out. On the contrary, he said, their virus writing strengthens the 'immune system' of the internet.

These moral nuances fall apart in the case of virus authors who are themselves willing to release worms into the wild. They're more rare, for obvious reasons. Usually, they are in countries where the police are less concerned with software crimes. One such author is Melhacker, a young man who reportedly lives in Malaysia and has expressed sympathy for Osama bin Laden. Anti-virus companies have linked him to the development of several worms, including one that claims to come from the 'al-Qaeda network'. Before the Iraq war, he told a computer magazine that he would release a virulent worm if the United States attacked Iraq, a threat that proved hollow. When I emailed him, he described his favourite type of worm payload: 'Stolen information from other people.' He won't say which of his viruses he has spread and refuses to comment on his connection to the al-Qaeda worm. But in December on Indovirus.net, a discussion board for virus writers, Melhacker urged other writers to 'try to make it in the wild' and to release their viruses in cybercafes, presumably to avoid detection. He also told them to stop sending in their work to anti-virus companies.

Mathieson wrote a critical response, arguing that a good virus writer should not need to spread his work. Virus authors are, in fact, sometimes quite aggrieved when someone puts a dangerous worm into circulation, because it can cause a backlash that hurts the entire virus community. When the Melissa virus raged out of control in 1999, many internet service providers shut down the websites of malware creators. Virus writers stormed online to pillory the Melissa author for turning his creation loose. 'We don't need any more grief,' one wrote.

If you ask cyberpolice and security experts about their greatest fears, they are not the traditional virus writers, like Mario or Philet0ast3r. For better or worse, those authors are a known quantity. What keeps anti-virus people awake at night these days is an entirely new threat: worms created for explicit criminal purposes.

These began to emerge last year. Sobig in particular alarmed virus researchers. It was released six separate times throughout 2003, and each time the worm was programmed to shut itself off permanently after a few days or weeks. Every time the worm appeared anew, it had been altered in a way that suggested a single author had been tinkering with it, observing its behaviour in the wild, then killing off his creation to prepare a new and more insidious version. 'It was a set of very well-controlled experiments,' says Mikko Hypponen, the director of anti-virus research at F-Secure, a computer security company. 'The code is high quality. It's been tested well. It really works in the real world.'

By the time the latest variant, Sobig.F, appeared in August, the worm was programmed to install a back door that would allow the author to assume control of the victim's computer. To what purpose? Experts say its author has used the captured machines to send spam and might also be stealing financial information from the victims' computers.

No one knows who wrote Sobig. The writers of this new class of worm leave none of the traces of their identities that malware authors traditionally include in their code, like their screen names or 'greetz', shout-out hellos to their cyberfriends. Because criminal authors actively spread their creations, they are cautious about tipping their hand. 'The FBI is out for the Sobig guy with both claws, and they want to make an example of him,' David Perry notes. 'He's not going to mouth off.

Dunham of iDefense says his online research has turned up 'anecdotal evidence' that the Sobig author comes from Russia or elsewhere in Europe. Others suspect China or other parts of Asia. It seems unlikely that Sobig came from the US, because American police forces have been the most proactive of any worldwide in hunting those who spread malware. Many experts believe the Sobig author will release a new variant sometime this year.

Sobig was not alone. A variant of the Mimail worm, which appeared last spring, would install a fake pop-up screen on a computer pretending to be from PayPal, an online e-commerce firm. It would claim that PayPal had lost the victim's credit card or banking details and ask him to type them in again. When he did, the worm would forward the information to the worm's still-unknown author. Another worm, called Bugbear.B, was programmed to employ sophisticated password-guessing strategies at banks to steal personal information. 'It was specifically designed to target financial institutions,' said Vincent Weafer, senior director of Symantec.

The era of the stealth worm is upon us. None of these pieces of malware was destructive or designed to cripple the internet with too much traffic. On the contrary, they were designed to be unobtrusive, the better to secretly harvest data. Five years ago, the biggest danger was the 'Chernobyl' virus, which deleted your hard drive. But the prevalence of hard-drive-destroying viruses has steadily declined to almost zero. Malware authors have learned a lesson that biologists have long known: the best way for a virus to spread is to ensure its host remains alive.

'It's like comparing Ebola to Aids,' says Joe Wells, a founder of WildList, a long-established virus-tracking group. 'They both do the same thing. Except one does it in three days and the other lingers and lingers. But which is worse? The ones that linger are the ones that spread the most.' The long years of experimentation have served as a sort of Darwinian evolutionary contest, in which virus writers have gradually worked out the best strategies for survival.

Given the pace of virus development, we are probably going to see even nastier criminal attacks in the future. Some academics have predicted the rise of 'cryptoviruses', malware that invades your computer and encrypts all your files, making them unreadable. 'The only way to get the data back will be to pay a ransom,' says Stuart Schechter, a doctoral candidate in computer security at Harvard.

This new age of criminal viruses puts traditional malware authors in a politically precarious spot. Police forces are under more pressure than ever to take any worm seriously, regardless of the motivations of the author.

A young Spaniard named Antonio discovered that last year. He is a quiet 23-year-old computer professional who lives near Madrid. Last August, he read about the Blaster worm and how it exploited a Microsoft flaw. He became intrigued and after poking around on a few virus sites, found some sample code that worked the same way. He downloaded it and began tinkering to see how it worked.

Then on 14 November, as he left to go to work, Spanish police met him at his door. They told him the anti-virus company Panda Software had discovered his worm had spread to 120,000 computers. When Panda analysed the worm code, it quickly discovered that the program pointed to a site Antonio had developed. Panda forwarded the information to the police, who hunted Antonio down via his internet service provider. The police stripped his house of every computer and threw Antonio in jail. After two days, they let him out, upon which his employer fired him. 'I have very little money,' he said when I met him. 'If I don't have a job in a little time, in a few months I can't pay the rent. I will have to go to my parents.'

The Spanish court is currently considering what charges to press. Antonio's lawyer, Javier Maestre, argued that the worm had no dangerous payload and did no damage to any of the computers it infected. He suspects Antonio is being targeted by the police, who want to pretend they've made an important cyberbust, and by an antivirus company seeking publicity.

Artificial life can spin out of control, and when it does, it can take real life with it. Antonio says he did not actually intend to release his worm at all. The worm spreads by scanning computers for the Blaster vulnerability, then sending a copy of itself to any open target. Antonio maintains he thought he was playing it safe, because his computer was not directly connected to the internet. His roommate's computer had the internet connection, and a local network, a set of cables connecting their computers together, allowed Antonio to share the signal.

But what Antonio didn't realise, he says, was that his worm would regard his friend's computer as a foreign target. It spawned a copy of itself in his friend's machine. From there, it leapfrogged on to the internet - and out into the wild. His creation had come to life and, like Frankenstein's monster, decided upon a path of its own.

© New York Times

Have your say: Virus writers - artists or vandals?