A SELF-PROCLAIMED leader of the international hacking ring Lulzsec has allegedly broken into a website belonging to a local authority in northwestern NSW.

Matthew Trevor Flannery, 24, from the Central Coast, is accused of gaining unauthorised access to, and altering, restricted data on Narrabri Shire Council's website in mid-April.

He also uploaded a file which disrupted the site's function, according to police documents tendered during Flannery's brief first appearance at Sydney's Central Local Court on Wednesday.

Flannery, who used the online handle Aush0k, did not enter a plea to three separate charges of unauthorised access to and modification of computer data.

The charges, if proven, carry a maximum penalty of 12 years in jail.

The case was adjourned to Woy Woy Local Court on August 6, with Flannery's bail continued until that date.

Sporting a dark pinstripe suit, the blond-headed, pale-skinned alleged hacker made no comment as he left court.

His arrest by Australian Federal Police officers on April 23 sparked headlines around the world after he told detectives he was a leader of Lulzsec.

The group, said to be an offshoot of the Anonymous hacking collective, claimed credit for a short but relatively disruptive series of attacks in 2011, including against America's CIA and the UK's Sun newspaper.

The veracity of Flannery's claim to head Lulzsec, which announced it was ceasing operations in 2011, remains unclear.

At the time of the Narrabri attack, he was working in Sydney as an overnight IT help desk assistant, employed by Content Security in North Ryde to provide advice to a US client.

It also remains unclear why he allegedly targeted a shire council 520km away, in the heart of the state's cotton farming community.

The region's most recent claim to fame was the unlikely selection of Wee Waa, a small town near Narrabri, to host the global album launch of French electro pop act Daft Punk in May.

AAP md

Originally published as 'Lulzsec leader' appears in Sydney court