10 Gary McKinnon
Gary McKinnon was an unemployed computer systems administrator when he, in 2001, began accessing computer systems belonging to the US military. He deleted important OS files and the US government claimed that he had caused hundreds of thousands of dollars worth of damage to systems that controlled missiles and important information as he searched for information on free energy and UFOs. According to the officials, this was the biggest ever attack on computer systems in America by a single person.
He was indicted by a grand jury and faced extradition to the United States from the United Kingdom, although this was eventually blocked in 2012 after years of legal proceedings as medical experts claimed that he had Asperger’s syndrome and would likely try to commit suicide if forced to go to the US.
9 Michael Bevan & Richard Pryce
In 1996, two British boys began to illegally access computer systems belonging to the United States Air Force, NASA and NATO. This caused widespread damage to those systems as files were deleted and moved. The attacks also came at a significant cost as experts in the US military attempted to stop the intrusion and block further attempts. Later, the pair also hacked into a research facility in Korea and dumped information about nuclear programs onto USAF severs in a move that could have led to armed conflict if North Korean data had been stolen as they would have immediately suspected the US and launched retaliatory attacks. Luckily for everyone involved, the moved information was actually South Korean and thus the US government was able to solve the international incident relatively easily.
8 Kevin Mitnick
One of the most famous hackers of all time, Kevin Mitnick was responsible for hacking into a wide range of computer systems and servers across several years. Primarily, he would hack into the systems of telephone and computer companies, copy confidential information and alter important data within the computer servers. He also managed to break into private email accounts by stealing passwords and was able to read the contents, becoming the most wanted computer fugitive in the US before he was apprehended in 1995. He now works in the security industry, helping websites and companies to block hacking attempts on their hardware.
7 Vladimir Levin
While many hackers target military or company computer systems in order to find out information or as a form of protest, others target customer accounts to benefit themselves. Vladimir Levin did exactly that in 1994, when he managed to access the Citibank network where he was able to steal more than $10 million from accounts. The Russian hacker was eventually arrested in the UK and extradited to the US where he spent three years in prison, while Citibank managed to recover all but $400,000 of the stolen funds. What happened to the money that wasn’t recovered is a mystery that has yet to be solved.
6 Michael Calce
More commonly known as MafiaBoy, Michael Calce was a high school student in Quebec, Canada, who managed to hack into some of the most visited websites on the internet in 2000. During a series of denial-of-service attacks, Calce was able to bring down the websites Yahoo!, FIFA, Amazon, Dell, eBay and CNN for several hours each, causing damage to their computer systems. The overall cost of his actions was said to be $7 million by prosecutors, although analysts estimate the attacks could have caused up to $1 billion in global economic damages.
5 Jeanson James Ancheta
A common form of hacking involves taking over other users’ computers in order to use them for other criminal activities. This is known as a botnet and is generally used to attack websites and computer systems, with the sheer number of computers being used making it incredibly difficult to defend against. Over the course of a year, Ancheta was able to hijack around 500,000 machines and hire out his services to those who wanted to take down particular websites. He was eventually caught in an FBI sting operation and was sentenced to 60 months in prison.
4 Adrian Lamo
In order to help hide his identity and make it difficult for authorities to track down who was responsible for attacks, Adrian Lamo would routinely use public computers at libraries and internet cafes to carry out his hacking. He had high profile targets that included Microsoft, Worldcom, AOL, The New York Times and Yahoo!, and would intrude on their computer systems where he would steal information and alter data. He was later charged by the FBI with computer crimes. In 2010, Lamo was also responsible for informing the US Army about Chelsea Manning’s leaking of more than 250,000 documents.
3 Owen Walker
Otherwise known as AKILL, Owen Walker was a highly skilled hacker who orchestrated attacks on a number of websites and computer systems over the course of several years. He was primarily responsible for creating the Akbot virus which allowed him to take control of millions of computers around the world and use them to launch attacks on particular targets. Experts estimate that the financial damage caused by the virus and his subsequent hacks could have been as high as a staggering amount of $26 million.
2 Albert Gonzalez
Cuban born Albert Gonzalez was responsible for carrying out the largest theft of credit card and ATM numbers from 2005 to 2007. In that time, authorities believe that Gonzalez stole more than 170 million individual card details by injecting various pieces of code into computer systems he had illegally accessed. He then used the stolen data to authorize fraudulent transactions and withdraw money from the accounts. Altogether, Gonzalez reportedly managed to cause around $200 million worth of damage through harm to computer systems and theft of cash.
Although the real name of this hacker has never been officially released, Greek police did reveal that he was a 58-year-old mathematician who was living in Athens. The man had been wanted for various computer crimes since 2002 but came under further scrutiny in 2005 when he hacked into the systems of Dassault, a French military company. He then stole sensitive information on weapons, aircraft and other technology before selling it on to other parties. Prosecutors argued that the hacker had caused upwards of $360 million worth of damage to Dassault.