YOU’RE PROBABLY SCARED of hackers.

And who wouldn’t be? They have the ability to topple corporations, send stock prices reeling, ruin your personal credit, and distribute false news stories, sending us all into the streets in a War of the Worlds–like panic.

But that’s not the whole story. Hackers gave us the Apple computer. They’ve improved Internet security. They fought for civil liberties on the Internet. They gave Ferris Bueller his day off.

There are all kinds of people who classify themselves as hackers, ranging from mild-mannered, law-abiding programming geeks to credit-card thieves with organized-crime connections. They’re a fractious community — usually male and in their late teens to early 20s, with a cavalier attitude toward Internet law. And it’s a community that now finds itself at the center of a renewed debate over the nature of the Internet as a free system. In the post–September 11 world, utopian dreams of an information democracy have been supplanted by fear of the Net’s power to cause harm. As a result, calls for regulating the Internet have accelerated, and advocates of freedom in cyberspace have been pushed to the margins. It’s a new World Wide Web out there.

BOB IS NOT your average high schooler.

Recently, the 17-year-old student hacked into a major Hollywood studio’s computer system and stole a copy of a yet-to-be-released blockbuster movie. As a result, he is one of only a few people who saw the original cut, complete with the line "man chowder," a potentially classic catch phrase that ended up on the cutting-room floor.

Bob — whose name was changed for this article — plays in a band, writes brilliant computer programs, and used to count himself a member of the "cyberpunks," the vandals of the computer world. When he talks about computers, his speech quickens as his mouth struggles to keep up with his brain. "We used to break into the elementary-school computers to try and change grades, and if we didn’t like people, we’d put fines on their library books," he says. "It would mainly be me and friends who didn’t know anything about computers. They’d be looking over my shoulder and chanting ‘Bob! Bob! Bob!’ "

He has an illustrious reputation as a hacker, but Bob relates his conquests, such the "man chowder" anecdote, with an air of detached amusement and a notable lack of bravado. So why did he do it? "Definitely for the challenge," Bob explains. "It’s a thrill — it’s like skydiving or something. You know, that falling feeling like when you’re in a roller coaster or something, when you’re in there covering your tracks, trying not to get caught."

Legendary hacker Lloyd Blankenship described that feeling of exhilaration in 1986 in an unofficial hacker manifesto (known as Conscience of a Hacker) that’s been circulating on the Internet for years. Blankenship describes the sensation of hacking as "rushing through the phone like heroin through an addict’s veins, an electronic pulse is sent out, a refuge from the day-to-day incompetencies is sought ... a board is found. ‘This is it ... this is where I belong.’ "

Indeed, for teenage hackers, it’s all about belonging. To gain acceptance by the elitist cyberpunk subculture, some young hackers commit risky and damaging crimes. Low-level, less skilled hackers (derided as "script kiddies") often vandalize Web sites or steal personal information to impress their friends and other hackers. But the criminal element is the exception, not the rule. Law-enforcement authorities say criminal hacker activity is rarely reported.

Hacker organizations, such as local chapters of the hacker organization the 2600 Group, tend to operate under the radar. They are part of an international movement loosely organized around 2600: The Hacker Quarterly, a magazine about the computer underground. They hold monthly meetings, billed as "forums for all interested in technology to meet and talk about events in technology-land, learn, and teach."

2600 meetings greatly resemble the geek table in the high-school cafeteria. One of the hackers plays with some scrapped hard drives. At the other end of the table, some take a surreptitious digital picture of a security guard. They talk about wireless Ethernet nodes around town. They swap code. There’s a moment of excitement when one of them causes a system crash and restart on his cell phone. At one point, a newcomer to the group says he’s not sure if he really qualifies as a hacker. Tami Friedman, a veteran member, administers a quick hacker test: "If a program doesn’t work the way you want it to, do you fix it? Do you stay up all night writing code? Do you read the manual before you start using new software?"

As in any clique, especially one considered "outcast," there’s a real bond among members of the 2600 Group, and they can quote Conscience of a Hacker from memory: "We explore ... and you call us criminals. We seek after knowledge ... and you call us criminals. We exist without skin color, without nationality, without religious bias ... and you call us criminals."

In the current political climate, the "criminal" label is more apt than ever.