An unemployed truck driver who allegedly gave himself the online nickname 'Evil' has been refused bail over what police say could have been Australia's biggest hacking attack.

David Cecil, 25, appeared in court in the New South Wales town of Orange to face more than 40 charges related to an alleged attempt to hack into the systems of Platform Networks, one of the 13 service providers for the National Broadband Network (NBN).

Australian Federal Police officers arrested Cecil yesterday at his home in Cowra after a six-month investigation which they say began when he started bragging about his plans in an internet chat room.

Police say Cecil was working alone and could have caused considerable damage to Platform Networks' systems and to those of other companies.

But they say the attack did not have the potential to cause serious disruption to the $36 billion NBN.

Platform Networks is an internet provider selling wholesale access to the NBN.

"What he'd basically done is that he'd tunnelled into their [Platform Networks'] system, he had bypassed their firewalls, he'd also bypassed all of their security systems," Assistant Commissioner Neil Gaughan told ABC TV's 7.30.

"So he was in the position where he was mapping their infrastructure, which enabled him, if you like, to be in a position to compromise not only the network more broadly, but also the system where he could basically collapse it if it seemed necessary to do so."

AFP commander Grant Edwards says the NBN was never on the verge of collapse because of Cecil's actions.

Police allege that Cecil is a self-taught hacker and police say he spent up to 20 hours a day on his home computer as he worked on the attack.

They say a number of companies may have been compromised but do not believe that personal information has been accessed.

Cecil has been charged with 48 counts of unauthorised access to, or modification of restricted data. He has also been charged with one count of unauthorised modification of data to cause impairment.

He has been held in custody to appear in court again on Friday.

Tip-off

Police have told the ABC their interest was triggered following a tip-off related to an investigation into an attack on a university website and another on a Melbourne company.

"We then obtained warrants through the courts to actually monitor his internet traffic obviously, and also monitor his voice communications," Commissioner Gaughan said.

"Basically what we were doing was seeing what he was doing as he was attacking different companies, and of particular note ... Platform Networks."

"Platform Networks is basically a distributed IT company, if you like, that actually hosts domain names for other services.

"So if you like, 'www.whatever' - they host those particular companies. So potentially, any customer of Platform Networks could have actually lost their web services for a period of time, if not indefinitely, depending on the security back-up that they had in place."

In a world where cyber attacks are becoming commonplace, police say this one stands out.

They cannot say what, if anything, the alleged hacker has done with his access, but they say he has been keen to highlight his activities.

"He's bragging quite broadly in the internet community that he is actually inside this particular company," Commissioner Gaughan said.

"We believe, and again we won't really know until we've had a chance to speak to him, that he's actually intentionally bragging on the internet and doesn't want to actually take it down because his - you know, control is power if you like and at this stage he's controlling that system."

'Good news story'

"The systems that we basically were monitoring and watching were being monitored the entire time," Platform Network's managing director David Hooton said.

"So from our perspective, yes we were well aware he was in control of those individual systems, but the actual criticality of those systems to our network were actually fairly insubstantial.

"It's certainly not ideal, however, we've been able to assist the Federal Police in protecting a fairly large number of businesses in Australia and overseas so it's obviously a good news story for everybody.

"These sorts of things happen on pretty much every large internet network on a daily basis so this is something which we deal with on a pretty regular basis."

Mr Hooton declined to discuss how the company planned to defend itself against future hacking.

"That's something which is an operational security item that we can't really discuss. Privacy-wise there's certainly not been any issues at all. This has been basically DNS servers and items which have been not containing customer data at all.

"From this perspective we've been learning that we've got a very good relationship with the Federal Police and that when we work together we can have a good outcome."

The AFP is planning to conduct a forensic examination of the alleged hacker's computers.