1. Kevin Mitnick

He’s one of the famous hackers or probably the most famous of his generation, Mitnick has been described by the US Department of Justice as ‘the most wanted computer criminal in United States history.’

The self-styled ‘hacker poster boy’ allegedly hacked into the computer systems of some of the world’s top technology and telecommunications companies including Nokia, Fujitsu and Motorola.

After a highly publicized pursuit by the FBI, Mitnick was arrested in 1995 and after confessing to several charges as part of a plea-bargain agreement, he served a five year prison sentence.

He was released on parole in 2000 and today runs a computer security consultancy.

He didn’t refer to his hacking activities as ‘hacking’ and instead called them ‘social engineering’.

2. Kevin Poulson

Poulson first gained notoriety by hacking into the phone lines of Los Angeles radio station KIIS-FM, ensuring he would be the 102nd caller and thus the winner of a competition the station was running in which the prize was a Porsche.

Under the hacker alias Dark Dante, he also reactivated old Yellow Page escort telephone numbers for an acquaintance that then ran a virtual escort agency.

The authorities began pursuing Poulson in earnest after he hacked into a federal investigation database.

Poulson even appeared on the US television Unsolved Mysteries as a fugitive – although all the 1-800 phone lines for the program mysteriously crashed.

Since his release from prison, Poulson has reinvented himself as a journalist.

3. Adrian Lamo

Adrian Lamo was named ‘the homeless hacker’ for his penchant for using coffee shops, libraries and internet cafés as his bases for hacking.

Most of his illicit activities involved breaking into computer networks and then reporting on their vulnerabilities to the companies that owned them.

Lamo’s biggest claim to fame came when he broke into the intranet of the New York Times and added his name to their database of experts.

He also used the paper’s LexisNexis account to gain access to the confidential details of high-profile subjects.

Lamo currently works as a journalist.

4. Stephen Wozniak

Famous for being the co-founder of Apple, Stephen ‘Woz’ Wozniak began his ‘white-hat’ hacking career with ‘phone phreaking’ – slang for bypassing the phone system.

While studying at the University of California he made devices for his friends called ‘blue boxes’ that allowed them to make free long distance phone calls.

Wozniak allegedly used one such device to call the Pope. He later dropped out of university after he began work on an idea for a computer.

He formed Apple Computer with his friend Steve Jobs and the rest, as they say, is history.

5. Loyd Blankenship

Also known as The Mentor, Blankenship was a member of a couple of hacker elite groups in the 1980s – notably the Legion Of Doom, who battled for supremacy online against the Masters Of Deception.

However, his biggest claim to fame is that he is the author of the Hacker Manifesto (The Conscience of a Hacker),

which he wrote after he was arrested in 1986.

The Manifesto states that a hacker’s only crime is curiosity and is looked at as not only a moral guide by hackers up to today, but also a cornerstone of hacker philosophy.

It was reprinted in Phrack magazine and even made its way into the 1995 film Hackers, which starred Angelina Jolie

6. Michael Calce

Calce gained notoriety when he was just 15 years old by hacking into some of the largest commercial websites in the world.

On Valentine’s Day in 2000, using the hacker alias MafiaBoy, Calce launched a series of denial-of-service attacks across 75 computers in 52 networks, which affected sites such as eBay, Amazon and Yahoo.

He was arrested after he was noticed boasting about his hack in online chat rooms.

He was received a sentence of eight months of ‘open custody,’ one year of probation, restricted use of the internet, and a small fine.

7. Robert Tappan Morris

In November of 1988 a computer virus,which was later traced to Cornell University, infected around 6,000 major Unix machines, slowing them down to the point of being unusable and causing millions of dollars in damage.

Whether this virus was the first of its type is debatable.

His public record, is that, its creator, Robert Tappan Morris, became the first person to be convicted under the Computer Fraud and Abuse Act.

Morris said his ‘worm’ virus wasn’t intended to damage anything and was instead released to gauge the size of the internet.

This assertion didn’t help him, however, and he was sentenced to three years probation, 4000 hours of community service and a hefty fine.

A computer disk containing the source code for the Morris Worm remains on display at the Boston Museum of Science to this day.

8. The Masters Of Deception

The Masters Of Deception (MoD) were a New York-based group of elite hackers who targeted US phone systems in the mid to late 80s.

A splinter group from the Legion Of Doom (LoD), they became a target for the authorities after they broke into AT&T’s computer system.

The group was eventually brought to heel in 1992 with many of its members receiving jail or suspended sentences.

9. David L. Smith

Smith is the author of the notorious Melissa worm virus, which was the first successful email-aware virus distributed in the Usenet discussion group alt. sex.

The virus original form was sent via email. Smith was arrested and later sentenced to jail for causing over $80 million worth of damage.

10. Sven Jaschan

Jaschan was found guilty of writing the Netsky and Sasser worms in 2004 while he was still a teenager.

The viruses were found to be responsible for 70 per cent of all the malware seen spreading over the internet at the time.

Jaschan received a suspended sentence and three years probation for his crimes. He was also hired by a security company.