Hackers are individuals who use their knowledge of computers to infiltrate and compromise the security of other computer networks. There are a number of reasons why people are inclined to hack into computers, from the benign to the malicious – anything from playing a simple prank to stealing millions of dollars. Hackers can work alone or in groups, and in a lot of cases are self-taught. In the United States, hacking is an offense under the federal Computer Fraud and Abuse Act and also subject to individual state law.
However the term "hacker" is one that is disputed among technology specialists and its meaning has changed over the decades. In the early days of computer science, a hacker was simply a name for a programmer developing technology in an academic environment – the only place where there would be access to computers. "New school" hackers in the 1980s and 1990s with access to their own home computers became a flourishing subculture. The Conscience of the Hacker, or The Hacker's Manifesto written under the pseudonym of ‘The Mentor' still inspires bedroom hackers today. "Yes, I am a criminal," he wrote. "My crime is that of curiosity…My crime is that of outsmarting you, something that you will never forgive me for." The American Criminal Law Review recognizes the varying degrees of computer crime and says the spreading of viruses, worms, Trojan horses, logic bombs, sniffers, and distributed denial of service attacks are usually undertaken by those motivated by malice or mischief rather than financial gain. It states computer criminals of this kind can be "youthful hackers, disgruntled employees and company insiders, or international terrorists and spies".
Hacking came to mainstream attention with the 1983 movie War Games, the story of a high school student played by Matthew Broderick, who nearly starts World War III from his bedroom. In the 1990s, the romanticized idea of the hacker as a loveable rogue was the inspiration for movies including The Matrix, Sneakers and Hackers, and for conspiracy theorist group The Four Horsemen in the TV series The X Files.
Mary L Radnofsky, author of Corporate and Government Computers Hacked by Juveniles, a 2006 research paper with the ominous sub-title Your Government Computer Is Being Targeted for a Hack Right Now. The Hackers Are Teenagers. They'll Never Be Caught, and They Know It, wrote: "Many such crimes are committed by students—not because they really want state secrets, but just to prove they can do it. Many more do it for the millions of dollars they can generate through extortion."
In 1988, hacker Robert Morris devised the "internet worm", a self-replicating virus that spread so quickly through computers it shut down the entire network for two days. Even back in 1998, hacking groups claimed that should they so wish, they could shut down the entire internet in half an hour. Viruses can spread across the world in hours, causing billions of dollars of damage through lost data and productivity. In the 21st century, hacking became political in nature; in 2001, Chinese hackers infiltrated American government computers in a co-ordinated attack in retaliation for the death of a Chinese pilot in a spyplane collision. With this politicization of hacking, it is increasingly regarded as a weapon in the arsenal of "cyber terrorists".
One of the most high profile cases of hacking is that of Gary MacKinnon, who managed to break into NASA and Pentagon computers in 2002. US authorities accused him of stealing hundreds of passwords, deleting files and shutting their whole system down for 24 hours. McKinnon, diagnosed with Asperger's syndrome, did it all from his bedroom in London, England – having taught himself to hack, inspired as a child by War Games. Where McKinnon described himself as a "bumbling computer nerd", the United States government considered his actions "the biggest military hack of all time". He faced 60 years in prison.
Supporters argue that despite the inconvenience hackers can cause to the systems of businesses – often targeting the biggest companies in the world, like AT&T and, ironically, Microsoft – highlighting these security gaps ultimately helps to make the internet safer. This has also been Gary McKinnon's defense for his hacking of the Pentagon computers: "I was amazed at the lack of security," he said. "The reason I left not just one note, but multiple notes on multiple desktops was to say, ‘look, this is ridiculous'." Businesses are increasingly employing "ethical hackers" to test their online security systems and keep ahead of threats.