Accused NSW hacker was 'thoroughly vetted'

A NSW man who allegedly hacked a government website and claimed to lead an international hackers' group was thoroughly vetted, his former employer says.

THE self-proclaimed leader of an international hacking ring was working as an overnight IT help-desk assistant for a US firm when he allegedly broke into and defaced an Australian government website.

Matthew Flannery, 24, was arrested on Tuesday night at the offices of Content Security in North Ryde, northwest Sydney, where he was a probationary employee, after a two-week intelligence-led investigation by Australian Federal Police.

The alleged hacker, known by the online handle Aush0k, was already being monitored by overseas police and is accused of breaking into a federal government website earlier this month.

Mr Flannery, from Point Clare on NSW's central coast, is alleged to have altered data on the site and posted an image on its front page.

He was charged with three counts of hacking activity - offences carrying a maximum combined penalty of 12 years in jail.

He was given conditional bail to appear at Woy Woy Local Court on the central coast on May 15.

Content Security said Mr Flannery had been thoroughly vetted before being employed as a "low-level" overnight help-desk assistant, offering advice for a US client.

"We did thorough background checks during his employment, as we do for all our prospective employees," the company said in a statement.

"The US company then came out and gave him and the rest of the help desk team training.

"Up until yesterday (Tuesday) he was still on probation."

Content Security insisted Mr Flannery did not use confidential data from within the company to carry out his alleged attack.

That was at odds with the AFP's belief that he used inside information.

"The AFP believes this man's skill sets and access to this type of information presented a considerable risk to Australian society," said AFP cyber crime commander Glen McEwen.

Police refused to identify the website that was targeted, which is believed to belong to a state or local government agency that was a client of Content Security.

It remains unclear if Mr Flannery is, as he claimed to police, a senior member of the Lulz Security (LulzSec) hacking collective which carried out a relatively short but disruptive series of attacks in 2011, including on America's CIA.

The group's stated aim was to carry out attacks for laughs or "lulz", with little or no political motive.

"He was actually in forums being inhabited by LulzSec and there was no denials of his claims of being the leader," said AFP Detective Superintendent Brad Marden.

"He appears to be a very well-informed IT expert within a particular company.

"The company had no knowledge of his activities.

"But he is a well-respected person within the Anonymous community, within LulzSec and that side of the house."

Experts raised doubts about his claimed status within LulzSec.

"I'm sceptical at this stage," the technology academic and author Suelette Dreyfus told AAP.

"Some hackers tend to gild the lily a little bit."

A Twitter account linked to Anonymous also cast doubt on his status within LulzSec.