5. Robert Tappan Morris

One of the earliest known hackers was Robert Tappan Morris, creator of the “Morris Worm” – a virus that is said to have infected around 6,000 computers. He released it while studying at Cornell in 1988, and was apparently attempting to determine the size of the internet. An innocent enough aim, but he had made his worm death-proof and so it kept replicating itself into unwanted places. He was indicted under the Computer Fraud and Abuse Act and was the first person to do so. As with many of these hackers, his sentence was relatively light  – probation, community service and a fine – and he went on to found several companies in the computing sphere. 

 

4. Cody Kretsinger

Affiliated with the hacker group LulzSec, Cody Kretsinger is known to his fellow hackers as “Recursion”. He was convicted in 2013 for his part in a 2011 hack on Sony Playstation, where he managed to get 77 million people’s personal data and cause an outage on the network for 24 days. LulzSec  has often been accused of being childish and operating with no real motivation other than, as their name suggests, “the lulz”. They don’t often hack for financial gain – none of the 77 million had their identity stolen – and try to prove just how easy it is to get this kind of data. Kretsinger was granted another relatively light sentence, with only a year in prison for his crimes and many of LulzSec are still at large and operating. 

 

3. Jacob Appelbaum

Another hacker associated with WikiLeaks, this is a man with a troubled past. Given up for adoption by his parents he ended up in a children’s home and then later living with his heroin-addicted father and assorted other junkies. After such an unsettled childhood, he was encouraged to channel his energies into computing and he is now the American public face of WikiLeaks, a role that has seen him constantly detained and questioned at airports about his political views. He is also the spokesman for Tor technologies, which aid projects like WikiLeaks by diverting e-mails between several different countries. So an e-mail sent in America may go to three different servers before reaching Iraq, securing the location of both parties. Appelbaum has never convicted of hacking and now lives in Berlin but is obviously still considered a threat as he and his partner are apparently spied on as they sleep. Chilling…

 

2. Kevin Mitnick

The title of “World’s Most Dangerous Hacker” has been much contested. These final two hackers have both been given it at different points but Kevin Mitnick is now a respectable businessman specializing, as so many former hackers do, in improving the security of their clients’ firms. But this reform has come at the end of a 5-year prison sentence, itself stemming from the violation of a previous sentence (Mitnick committed a hack at the end of his supervised release period). He was arrested in 1995 after breaking into the Department of Justice computers and was said to be able to launch nuclear missiles by whistling down a payphone. The claims may have been exaggerated, but it’s easy to see why he was considered the most dangerous man in the world back in the 1990s.

 

1. Gary McKinnon

But Mitnick has since been superseded by McKinnon, who managed to hack into the Pentagon computers and leave the message “Your security is crap”. Between 2001 and 2002 – sensitive times for America – he repeatedly hacked US military and NASA computers from his base in London, deleting files and changing passwords. At one point he caused a 24-hour shutdown and caused munitions trucks to be stopped. He also left an anti-American message: “US foreign policy is akin to Government-sponsored terrorism these days … It was not a mistake that there was a huge security stand down on September 11 last year … I am SOLO. I will continue to disrupt at the highest levels.” He was arrested in 2002 and is currently imprisoned in Britain, although the US continues to request his extradition. A skilled but also very dangerous hacker who was stopped before he managed to cause a military disaster.