A self-proclaimed leader of the LulzSec international hacking group has been arrested in Australia, police said, charging him with attacking and defacing a government website.
The 24-year-old IT professional, who went by the online identity "ozshock", was seized at his office in a town 76 kilometres (47 miles) north of Sydney on Tuesday.
"The man is a self-proclaimed leader of the group Lulz Security (LulzSec), a computer hacking group that has existed since 2011," the Australian Federal Police said, adding that he was known to international police forces.
"It will be alleged that this person, known by the online identity ozshock, had gained unauthorised access and caused data impairment to a government website during this month."
LulzSec, an offshoot of the larger group Anonymous, has claimed responsibility for multiple cyber attacks, including against Sony Pictures, Rupert Murdoch's News International, and the CIA.
Police called the man, who has not been named, "a well-respected person within the Anonymous community, within LulzSec".
They added that he was employed "in a position of trust" at the company he worked for, although that company had no knowledge of his activities.
Australian Federal Police Cyber Crimes Commander Glen McEwen said the man's job gave him access to sensitive information, which allowed him to carry out the attack on the unnamed website.
"Police believe this man's skill sets and access to this type of information presented a considerable risk to Australian society," he told reporters.
"Our early intervention interrupted him before he could commit any further serious offences.
"But the ability to interrupt online trading, online transactions for governments, can have serious consequences in the long-term."
He has been charged with two counts of unauthorised modification of data to cause impairment and one count of unauthorised access to a restricted computer system and faces a maximum of 12 years in jail.
The man was released on bail and will face court in May.
Cyber attacks that LulzSec has taken credit for include an extensive breach of Sony Pictures computer system in 2011, which led to the personal data of thousands of Sony customers being posted online.
American Cody Kretsinger pleaded guilty to various charges related to that incident and was sentenced to one year in jail last week.
Last year, two British members of the group admitted carrying out attacks against the CIA and News International.