No one at IT giant IBM has been sacked or disciplined over the census debacle, but its managing director has unreservedly apologised for the stuff-up.
Kerry Purcell said his company, contracted by the Australian Bureau of Statistics to run the eCensus system, took full responsibility for its role in the bungle that forced a 40-hour shutdown of the website.
"The fact that the Australian public and a valued customer, the government, were inconvenienced does not sit well with us," he told a Senate inquiry in Canberra on Tuesday.
The incident could cost taxpayers up to $30 million, but IBM is in negotiations with Treasury Secretary John Fraser about covering some of the extra costs.
It was revealed a simple routine test before census night, when the system was hit with four distributed denial-of-service (DDoS) attacks, could have avoided the lengthy outage.
Following the fourth attack about 7pm, one of two routers did not restart properly because it was not correctly configured.
It then gave false information about foreign traffic that was trying to access the site, prompting the ABS to shut it down.
The company's chief engineer Michael Shallcross conceded the problem could have been detected earlier if the router was physically turned off and on again.
IBM defended the use of its geo-blocking solution, dubbed "Island Australia", to protect it from DDoS attacks.
It instead blamed Nextgen - one of two internet providers it contracted to control web traffic.
"We stand by... the view that geo-blocking is an effective DDoS attack prevention mechanism," Mr Purcell said.
However the prime minister's special advisor on cyber security, Alastair MacGibbon, said there were better alternatives.
He told the inquiry that relying solely on Island Australia was "clearly a failure".
"While this was a failure to deliver on the contractual obligations that IBM had, there was a failure on the part of ABS to sufficiently check that the contract had been delivered," Mr MacGibbon said.
"Had that checking been done, they may have discovered the hole in the Island Australia denial of service protection that leads us to be here today."
ABS chief David Kalisch said the outage tested the patience of Australian households and promised a more rigorous approach to the 2021 census.
"The ABS made a number of poor judgments in our preparation for the census that led to poor service experience by many households and I apologise to the community on behalf of the ABS," he said.
IBM, the ABS and Mr MacGibbon all stressed that no personal data was compromised during the incident.
An internal review, conducted by Mr MacGibbon, has been completed and is now with the prime minister.
