The 24-year-old IT worker was arrested in Sydney after he was linked to a recent cyber-attack against an Australian government agency.

The Australian Federal Police said the man was described as a leader on LulzSec chat sites and made no attempt to deny it. His online name was “OzShock”.

The hacking group – whose name derives from the term “laugh out loud” and “security” – is an offshoot of the well-known hacking group Anonymous and has been tied to attacks on the CIA, Sony Pictures, The Sun newspaper, the NHS and Nintendo. The group has also allegedly broken into Australian government and university sites.

“This person known by the online identity OzShock had gained unauthorised access and caused data impairment to a government agency this month,” said Commander Glen McEwan, from the AFP.