Crooks, nations could be cyber attackers

The prime minister's cyber security adviser says criminals or nation states could have been behind the denial of service attack on Australia's online census.

Alastair MacGibbon is heading an investigation into the attack on the census, which led to the Australian Bureau of Statistics taking its site offline before millions of Australians could enter their census data.

The former Australian Federal Police member told 2GB radio the person or persons behind the attack used United States networks, but he did not believe they were American.

"Yes, we have nation states, yes there are criminal groups, yes there are issue-motivated groups and then there are people who just like to show they are smarter than us," he told 2GB on Wednesday.

"I don't know which one of those four did what they did last night. I hope we know soon."

He said the "malicious person or persons" found a way into the ABS's system through a "misconfigured service in relation to geo-blocking", which was the first line of defence against intrusions from overseas sources.

Then a piece of computer hardware known as a router failed.

"There was some traffic they did not understand and they were worried that it could mean that someone was trying to steal the information, so they made the call to take this offline," he said.

The activity was subsequently found not to be malicious but the network was kept down in any case.