They move within a shadowy underworld using skills most of us could never acquire.
Some see themselves as crime fighters, battling injustice, corruption and oppression. Others are pranksters – the kind of people who set light to bridges just to watch them burn. Plenty more do it simply to steal and get rich.
Hacking is as old as computers, but the current wave of high-profile assaults across the globe has led to unprecedented interest in who hackers are and why they do what they do.
The Independent tracked down one prolific British hacker who is engaged in a personal cyber war against LulzSec, the collective behind a string of attacks on websites as diverse as the CIA's homepage, the Serious Organised Crime Agency, Fox TV and – most recently – the Arizona Police Department.
With secrecy a vital component of his work the hacker – who goes by the name TriCk – refused to meet in person. But through online chats he shone a light on a world of competing egos, where people living an online double life brush off the threat of capture, fuelled by the adrenaline rush that comes from hacking.
Currently studying at college, TriCk is in his late teens and lives with his parents who have little idea what he gets up to at night. "I started hacking when I was eleven," he says. "I got hacked on an online game I was playing and wanted to gain all my items back. The whole idea of knowing I shouldn't be doing something, or knowing I shouldn't be in someone's account, attracted me."
TriCk now works alongside two other hackers as part of a group called TeaMp0isoN who are well known in the underground hacking scene. Last December they broke into the servers of the English Defence League and published its membership list. They defaced the website of Indian politician Rahul Gandhi, leaving angry messages on human rights abuses in Kashmir.
Core members have known each other online for five years, but have never met. "We live two lives," says TriCk. "Online and offline. I know that sounds lame but that's how it is in the hacking scene."
The image of the hacker permanently glued to his or her computer and rarely seeing the sunlight is a common one. But TriCk is keen to play down any suggestion that hackers struggle to function in the real world.
"The majority of hackers live a perfectly normal life, but the one thing I've seen in the hacker community is the use of drugs and alcohol."
As a practising Muslim, he stays clear of substance abuse, but has no qualms about breaking the law and laughs at the idea he will be caught.
"It don't bother me," he writes. "I don't fear Mi5, the FBI or the CIA. I class them as thugs and criminals... I fear no-one except for God."
He says he's never used his hacking skills to profit financially, but he knows hackers who do steal.
"Money is not our motive," he says. "We're in it for knowledge, love of the art and to push our message out. But I know people who hack for money. Most of them come from Third World countries or are living in occupied/oppressed countries."
That's not an argument most law enforcement agencies would buy. This week the FBI said that – with help from international partners – it had disrupted a hacking network which raked in more than $74m (£46m) by spreading malware that infected computers and skimmed bank details.
Most arrests were made in Latvia and the Ukraine – hardly Third World or oppressive countries. In fact law enforcement agencies say a large chunk of financial hacking is run by mafia-style gangs that operate out of central and eastern Europe, many of whom are also implicated in drugs and human trafficking.
TriCk classes himself as a "black hat hactivist", a hacker who has no ethical issue with destroying networks or breaking into servers but does so to spread a political message.
"To me being a blackhat is causing destruction and being a hactivist is to oppose a certain ideology or raise awareness," he says.
Yet he has little time for rival hactivist groups like LulzSec and Anonymous who he dismisses as "script kiddies", a derogatory term used to describe people who use other hacker's tools to commit their break-ins. TeaMp0isoN and other hacking groups have turned their skills on LulzSec, breaking into web-pages that they say are run by the group's leaders and exposing their personal details. LulzSec says the hacks have got the wrong people.
"We have all the info and it will be in an e-zone exposing all LulzSec's members," says TriCk, declining to say when the info might be published. "We don't class [LulzSec or Anonymous] as hackers because we come from the real hacking scene. They are script kiddies and fame whores."
He says the media obsession with headline-grabbers like LulzSec is a handy diversion from underground hackers who can really do damage.
"If the world knew what underground hackers had access to, within 24 hours of knowing there would be a meeting of world leaders," TriCk says ominously as the chat session with The Independent comes to a close.