It was a hacker conference, so just about everyone was wearing a T-shirt. And most of the T-shirts had something to say. “Know Your Enemy,” said one, just beneath that familiar Microsoft Windows logo. “There’s no place like 127.0.0.1,” said another, recasting Dorothy Gale’s famous mantra with internet speak. “Stop laughing,” said a third. “Computers are cool now.” More Hacker Fun Why Hackers Are So Much Funnier Than You Are Greatest Geek License Plates Greatest Geek License Plates: Part II Some proclaimed a deep devotion for things like open source software and public key encryption. Some carried rather clever inside jokes that spoke only to other hackers. Some railed against the corporate world. Some insulted the government. And, yes, most of them were black. Brad Johnson was at the conference -- the fifth annual Hackers on Planet Earth, held on the west side of Manhattan in the summer of 2004 -- and when he decided to build a photo essay on these hacker T-shirts, it was bit a like shooting fish in a barrel — or squashing bugs in the Linux kernel. "It was what people were wearing," says Johnson, who co-wrote a book on the information revolution, Technomanifestos. Hackers have always had a particular affection for T-shirts. "It's the ubiquitous fashion choice among hackers -- all over the world," says Gabriella Coleman, an anthropologist who spent three years living with software hackers and documented the experience in a book called Coding Freedom: The Ethics and Aesthetics of Hacking. A T-Shirt is what you wear when you don’t want to look like The Man -- particularly a black T-shirt or a T-shirt that's old and threadbare -- and if you’re a hacker, that’s one of your main objectives. This is true whether you’re working on the Linux kernel or busting into somebody’s top secret server. "It's a way for them to signal that they don't care about fashion status in the way mainstream society does," says Coleman. "Of course, it then becomes its own form of fashion and status." Some hacker T-shirts are just T-Shirts, while others -- so many others -- are a way of proving your hacker credentials, a means of communicating with other hackers. This includes shirts from conferences and other meetups you've attended over the years, but it also includes shirts that deliver an added message. Sometimes, this message is built on humor — another indelible part of hacker culture. Sometimes, it carries at least the semblance of disgust, as it takes a swipe at someone like Bill Gates or Dick Cheney. And sometimes, it’s a mixture of the two. The quintessential example is the “OS Wars” T-shirt that appeared at an Atlanta Linux conference in the late '90s (see above). Yes, the shirt recast the leaders of the open source movement as characters from Star Wars. Linux Torvalds, the creator of Linux, was Luke Skywalker. Alan Cox, his right-hand hacker, was Princess Leia. Eric Raymond, author of open source tome The Cathedral and the Bazaar, was C-3PO. And the Free Software Foundation’s Richard Stallman doubled as R2-D2. Naturally, this meant that Microsoft founder Bill Gates appeared as Darth Vader. The shirt delivered the kind of inside joke that hackers so enjoy — and it took a swipe at Microsoft. But it also rearranged an existing cultural image — another common theme among hacker T-shirts. Hackers like to hack images in much the same way they hack software. But this is just one shirt among so many. Here, we give you a list of our favorites, including everything from the iconic UNIX T-shirt to the inevitable “Keep Calm and Code On” (click on thumbnail images above). No doubt, you will wail in anger that we’ve missed some — or many. But that’s OK. We’ll do this again. Please e-mail us with your suggestions to cade_metz@wired.com. You’re not a hacker? You’ll enjoy the list too. But you should brush up on your binary. Photos: Russ Nelson Additional reporting by Robert McMillan

The "OS Wars" T-shirt is a thing of the past. Even Eric Raymond tell us he no longer has one. But the trope lives on. Photo: Kent Chen

A nice play on words. And another swipe at Microsoft. Photo: Zopeuse

Why stop at the destruction of Microsoft? Let's go whole hog! Photo: Zopeuse

Patty Hearst ain't got nothin' on the penguin. Photo: Zopeuse

Yes, hacker T-shirts can be clever without calling for the destruction of the state. Used by UNIX and other UNIX-like operating systems -- such as Linux -- "sudo" is a command that lets you run an application under the security privileges of another user. Photo: The Linux Journal

Before Linux, there was UNIX, the seminal operating system built by Ken Thompson and Dennis Ritchie at Bells Labs in the late '60s and early '70s. And before all those Linux T-shirts, there was the UNIX shirt. The shirt pictured above arrived in 1985 to commemorate the tenth anniversary of Usenix -- the UNIX user group that eventually morphed into the broader association of hardcore hacking types -- but the basic design dates all the way back to the mid-1970s, when it was cooked up by an early UNIX guru named Mike O'Brien. The image on the shirt is the handiwork of Phil Foglio, who would eventually find fame in the art world. But in those days, O'Brien says, Foglio was just a "starving student fan artist." Foglio agreed to paint the image in exchange for certain services provided by O'Brien. Foligo's roommate had just left town without providing the combination to the wall safe in their apartment, and O'Brien was a bonded locksmith. "I think Phil's making the big time is less of a surprise to me than UNIX doing the same thing," says O'Brien, "at least as I saw the probabilities back then." Both made the big time -- and so did the shirt. The design became a staple at Usenix conferences for years to come. The image depicts a circa 1975 computer called the PDP-11/40 and the little red dudes are demons or, should we say, daemons. The red demon has long been the UNIX mascot -- because, well, UNIX relies on little background programs known as daemons. Photo: Kirk McKusick

And the UNIX shirt lives on. This photo was snapped in Germany in 2002, at an annual meetup of the SETI@Home project, an effort to discover extraterrestrial life using extra processing power from the world's personal computers. UNIX isn't really his country. That's a metaphor. C is indeed a language -- but of the programming variety. Photo: Zanthia

Before UNIX, there was Multics, an operating system for time-sharing computers originally developed in the mid-1960s. This photo is from the annual Multics Picnic, held in Groton, Massachusetts in 1979. The two Multicians -- Rick and Katie Kissel, pictured with their son Jake -- worked at Honeywell's Cambridge Information Systems Laboratory, the center of Multics development. Katie's shirt reads: "Multics keeps it up longer." But that's just the text. We'll leave the subtext to you. Photo: Tom Van Vleck

A hacker T-shirt that predicted the future. TCP/IP is the set of protocols that drive the internet -- not to mention so many private networks -- and this T-shirt dates back to 1992, before the internet was the internet. Photo: Russ Nelson

As hacker watcher Gabriella Coleman points out, some hacker T-shirts are even illegal. Literally. This shirt -- from the mid-90s -- displays a small Perl program that can be used to encrypt and decrypt data. At the time, it was illegal to export such code outside the U.S., which is why hackers put it on a T-shirt and called themselves arms traffickers. "I have interviewed people who talk about the deep identification that comes when they were at the airport and they saw someone with this source code on their T-shirt," Coleman says. "It's doubly strong. They're not only part of the technical craft-hood. They also believe in the politics of free access -- and they're breaking the law." The same attitude would later spawn T-shirts printed with the DeCSS code needed to circumvent the copy protection software on commercial DVDs. In certain countries, including the U.S., publishing the code was against the law. Photo: Adam Back

How to hack the Calvin Klein logo. Photo: Brad Johnson http://www.kband.com/photo/5thhope/

This captures the hacker attitude rather nicely -- or not so nicely, depending on your perspective. Legend has it that this shirt was once banned at Google. But we hope that's not true. Photo: Russ Nelson

This is another T-shirt from the collection of Russ Nelson, who seemed to turn up at just about every Linux conference in the 90s -- and beyond. The shirt speaks the truth. Photo: Russ Nelson

This is how Linux hackers get drunk. Sort of. Photo: Kevin Key

The trouble with being a hacker is that people are always asking you for help with computers. But hackers also have a knack for telling people to go away -- with Perl code. Photo: Kevin Key

Perl code isn't the only method. Photo: Planetc1

You don't get this shirt? That's just what he's going for. And that binary shirt is paired with a binary watch. Yes, a binary watch. Photo: David Llloyd

Hackers also know how to slack off -- in style. Photo: Kevin Key

Then there are hackers that photograph themselves wearing hacker T-shirts. And, well, that's a hack too. Photo: Kevin Key