The alleged leader of the hacking group LulzSec, the collective which claimed responsibility for infiltrating the the CIA website, is being held by Australian police.
The 24-year-old computer expert, who held a position of trust in the IT department of an international company, was arrested at work in Sydney last night.
He has been charged with hacking offences that carry a maximum penalty of 10 years.
Take him away boys: Australian Federal policemen arrest the man they say is the self-proclaimed leader of the international hacking group LulzSec, the group that claimed responsibility for shutting down the CIA website
Glen McEwen, head of cyber crime operations at Australian Federal Police, said the man's job gave him access to sensitive information from clients including government agencies.
LulzSec, an offshoot of the better-known hacking collective Anonymous, has taken credit for hacking attacks on government and private sector websites.
Those hit include the Central Intelligence Agency (CIA), Sony Pictures, 20th Century Fox and Nintendo.
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Anonymous - and LulzSec in particular - became notorious in late 2010 when they launched what they called the 'first cyber war' in retaliation for attempts to shut down the Wikileaks website.
The name LulzSec is a combination of 'lulz', another way of writing 'lols' - an internet slang acronym standing for 'laugh out loud' - and security.
A tweet by Anonymous Australia denied that the suspect was part of their network
Australian police said the unnamed Australian man, who is believed to have used the online moniker 'Aush0k', was known to international law authorities.
However, a Twitter account claiming to represent Anonymous in Australia earlier today said the announcement by Australian Federal Police was 'bulls***'.
For the lulz: The logo of hackers' collective LulzSec, a group which has claimed responsibility for cyber attacks on public and private organisations
Responding to tweets asking if the individual was known to the hacking collective, Anonymous Australia responded: 'Nope not part of the usual suspects on any of our chans of communication I suspect some DDos skid on his mums win (Windows) box.'
Others on the social messaging site expressed doubt that groups like LulzSec have leaders in the sense claimed by Australian police.
The arrest comes a week after an American member of LulzSec, Cody Kretsinger, was convicted in a Los Angeles court and sentenced to a year in prison followed by home detention.
Kretsinger, who used the online handle 'Recursion', pleaded guilty in a plea agreement with prosecutors.
Court documents in that case revealed that Anonymous leader 'Sabu', whose real name is Hector Xavier Monsegur, had provided the FBI with information on fellow hackers after pleading guilty to hacking offences.
The Australian suspect has been charged with two counts of unauthorised modification of data to cause impairment and one count of unauthorised access to a restricted data system.
The charges relate to an attack on an Australian government website earlier this month.
Investigation: A forensics officer examines a computer while executing a search warrant following the arrest. Police said their suspect's job gave him access to sensitive information from clients including government agencies
Search: LulzSec, an offshoot of the better-known hacking collective Anonymous, has taken credit for hacking attacks on government and private sector websites
'Let me make it extremely clear to everybody out there, this is not harmless fun, this is serious,' said Mr McEwen at a press conference.
He said the man posted in online forums frequented by other members of LulzSec that he was the group's leader.
'There were no denials of his claims of being the leader,' said Mr McEwen.
The man has been granted bail and will appear before a court next month.
LulzSec allegedly broke into Australian government department and university websites in 2011.
Anonymous last year took around 10 Australian government websites offline, protesting plans to force ISPs to store more user data and make it available to security services.