Hector Xavier Monsegur, AKA Sabu, is one of the co-founders of the hacking group LulzSec. He's notorious not only for being a hacker, but also for being a double agent who worked for the FBI. He helped the agency identify other hackers.

Vladimir Levin is a Russian hacker who engineered a bank heist from St Petersburg. He and his accomplices were able to steal over 10 million from Citibank accounts by wiring it to other accounts in cities around the world. All except 400,000 of the stolen money was recovered.

Barnaby Jack was a New Zealand hacker who was famous for his demonstration of jackpotting 2 ATMs and making them spit out cash on stage during the Black Hat security conference in 2010. At another conference in 2011, he demonstrated how an insulin pump could be hacked into wirelessly and deliver a lethal dose. At yet another conference in 2012, he demonstrated how a victim could be assassinated by pacemaker hacking. Jack died a week before he was due to give a presentation at the Black Hat 2013 conference on medical device vulnerability.

David L Smith is the hacker who released the Melissa virus is 1999. This internet virus ended up clogging and shutting down email systems because it overloaded servers. It caused 80 million in damage, and cost Smith 20 months in jail time.

Albert Gonzalez is a notorious computer hacker who went by aliases like SoupNazi and KingChilli. Between 2005 and 2007 he masterminded the theft of more than 170 million credit and debit card numbers through the hacking of retail stores like DSW, Office Max, Boston Market, Barnes Noble, and TJ Maxx. Along with other cash, Gonzalez was found to have 1.2 million in a barrel buried in his parents' backyard.

He's best known for founding WikiLeaks, but Julian Assange was once an Australian teenage hacker known as Mendax. Later in life he admitted that "I am -- all hackers are, and I would argue all men are -- a little bit autistic." And he also admits that "It was certainly addictive. You'd dive down into a computer system -- typically, for me at the time, the Pentagon's 8th Command Group computers. You'd take it over, projecting your mind all the way from your untidy bedroom to the entire system along the halls, and all the while you're learning to understand that system better than the people in Washington. It was like being able to teleport yourself into the interior of the Pentagon in order to walk around and take charge."

Adrian Lamo has been dubbed the "Homeless Hacker" because he often did his hacking from coffee shops, libraries, and internet cafes. The New York Times busted him when he broke into their computer system and added his own name to their list of expert sources. He also used the newspaper's LexisNexis account to research high-profile subjects. Lamo also hacked into other computer networks, including Yahoo! and Microsoft. In 2010, Lamo gained even more notoriety, by turning in Pfc Bradley Manning for leaking hundreds of thousands of government papers to WikiLeaks.

Mike Calce -- AKA MafiaBoy -- was only 15 years old when he hacked into some of the world's largest online stores. His Valentine's Day, 2000 denial-of-service hack affected big names like Amazon, eBay, and Yahoo! Calce was busted when he bragged about his hacking in online chat rooms.

They're way more famous for co-founding Apple. But long before that, Steve Jobs and Steve Wozniak started out as hackers. It all began in 1971 on the day before 20 year old Steve Wozniak started college at Berkeley. He came across an article about phone phreaks -- and decided he wanted to be one too! So he called 17 year old Steve Jobs -- still a senior in high school -- to tell him all about it.Within a few months Wozniak had built his very own digital blue box to hack into the phone system and make free calls. The pair started selling blue boxes using the aliases Oaf Tobar Jobs and Berkeley Blue Wozniak. Wozniak was even able to get through to the Vatican using his box. "In this heavy accent I announced that I was Henry Kissinger calling on behalf of President Nixon. I said 'Ve are at de summit meeting in Moscow, and we need to talk to de pope."

Robert Tappan Morris is infamous for creating the Morris worm in 1988. The worm was the first virus of its kind to spread through the internet -- and it ended up disabling about 10 of computers that were hooked up to the internet at the time. According to Morris, he hadn't intended to cause any harm with his worm. Instead he claims that he released it to get an idea of the size of the internet. All the same, he ended up becoming the first person to be convicted via the Computer Fraud and Abuse Act. Morris is now a professor at MIT.

Bored at school, George Hotz once hacked several classroom computers to play Beethoven's 9th Symphony in unison. But his biggest claim to fame is being the first person to ever hack Apple's iPhone. The Jersey 17 year old figured out how to jailbreak his iPhone so it could be used with other cell phone carriers. He announced it on YouTube, saying "Hi, everyone, Im GeoHot. This is the worlds first unlocked iPhone. Since then, he's said "My whole life is a hack." Hotz went on to hack into the PS3 -- and got sued by Sony.

Jonathan James was only 15 years old when he hacked into Department of Defense computers. He even got hold of NASA source code that controlled temperature and humidity in the International Space Station. James was the first juvenile offender to be convicted of a cyber crime.

He's reinvented himself as a respected journalist who writes for Wired Magazine on the topic of computer security. But Kevin Poulson -- AKA Dark Dante -- first came to fame as a notorious hacker who took over the phone lines of KIIS-FM to be the 102nd caller and winner of a Porsche. He also went online to hack into FBI files. But when a story about his fugitive life of crime appeared on the TV show 'Unsolved Mysteries' -- all of the 1-800 call-in tip lines mysteriously crashed just as the phone number was displayed on the screen.

Kevin Mitnick was once the "World's Most Wanted" computer hacker. He was even put in solitary confinement because it was believed he might be able to start a nuclear war -- just by whistling into a phone. Mitnick allegedly hacked into the likes of Sun, Motorola, and Nokia. But he denies hacking NORAD and wiretapping the FBI. His favorite hack happened when he was still a kid. He took over a local McDonald's drive-through speaker. "I would sit across the street from McDonalds and I would take their order and tell them they were the 50th customer so your order is free. Please drive through your order is free. People would drive up to the window and I would say, Our weight detection system detected your car is a little heavy so we recommend the salad instead of the Big Mac.' But my favorite was when the police drove up and I would say, Hide the cocaine, hide the cocaine!'"

Scottish hacker Gary McKinnon is alleged to have committed the "biggest military computer hack of all time." The US government accused him of hacking into dozens of Army, Navy, Air Force, and Department of Defense computers in addition to 16 NASA computers. But McKinnon denies being a malicious hacker -- instead he calls himself a "bumbling computer nerd." He claims to have just been looking for evidence of UFOs. His goal was apparently to expose what he believed was the cover up of a US military reverse engineering of an anti-gravity propulsion system which they had allegedly recovered from alien spacecraft.