NYT Magazine: The Virus Underground. By Clive Thompson. Philet0ast3r, Second Part to Hell, Vorgon and guys like them around the world spend their Saturday nights writing fiendishly contagious computer viruses and worms. Are they artists, pranksters or techno-saboteurs?

This is how easy it has become.

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 favorite 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 neatly made 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 -- and out here in the countryside, surrounded by soaring snowcapped mountains and little else, he's bored a lot -- 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.

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