Australian Federal Police have arrested the self-proclaimed leader of the international hacking group LulzSec.
Police said the 24-year-old IT worker, who held a position of trust at an international company, was arrested in Sydney on Tuesday evening and charged with hacking offences that carry a maximum penalty of 10 years in prison.
Glen McEwen, manager of cyber-crime operations at Australian Federal Police, said the man was detained at work, where he had access to sensitive information from clients including government agencies.
LulzSec, an offshoot of the international hacking group Anonymous, has taken credit for hacking attacks on government and private sector websites, including the CIA, Sony Pictures, 20th Century Fox and Nintendo.
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" or "laugh out loud", and security.
Australian police said the unnamed Australian man, who used the online moniker "Aush0k", was known to international law authorities.
His arrest comes a week after an American member of LulzSec, Cody Kretsinger, was sentenced in a Los Angeles court 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 hacker 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 after a government website was attacked earlier this month.
"Let me make it extremely clear to everybody out there, this is not harmless fun, this is serious," McEwen said at a press conference.
McEwen 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," McEwen told reporters.
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 and 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.