The Australian Bureau of Statistics has continued its run of outs, scoring an own goal in the Census main event last night, after the agency claimed the site crashed thanks to four denial of service attacks.
"The 2016 online Census form was subject to four Denial of Service attacks of varying nature & severity," the ABS said on Twitter this morning.
"The first three caused minor disruption but more than 2 million Census forms were successfully submitted and safely stored. After the fourth attack, just after 7:30pm, the ABS took the precaution of closing down the system to ensure the integrity of the data."
"Steps have been taken during the night to remedy these issues, and we can reassure Australians that their data are secure at the ABS."
The agency said it would provide an update at 9am Wednesday.
The ABS has launched a joint investigation with the nation's defence intelligence agency into the assault, which ramped up on Tuesday evening as most of the population was going online to complete the survey.
"It was an attack," chief statistician David Kalisch told ABC radio on Wednesday. "It was quite clear it was malicious."
The source of the attacks is unknown but Kalisch said they came from overseas.
On Tuesday, Opposition Leader Bill Shorten said that once the Census is completed, the Australian government needs to discuss with parliament the increasing retention of names and address data, and the reasons it is being kept.
"I think we need to have a good, long look at the whole process to make sure we're not asking for information we don't need," he said. "And to reassure ourselves that what information that is stored, is stored securely."
The Opposition Leader said politicians committed to boycotting the Census were grandstanding.
The intrusions will put a spotlight on the federal government's AU$240 million cyber security strategy and the security of government resources online.
The ABS confirmed last week that its IBM-developed online Census forms would not be able to handle names with accents or ligatures.
The agency later removed a claim made by it that it was rated by the Australian National Audit Office as being in its "Cyber Secure Zone".
More on Census 2016