This was a big problem, as two-thirds of Australians were expected to fill out the census forms online this year. The census takes place every five years, and there are fines for not completing the forms.

According to the Australian Bureau of Statistics (ABS), the website successfully stood up to three denial-of-service attacks during the day—such attacks flood the target’s servers with connection requests until they are overloaded and shut down.

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Then a fourth attack hit, just after 7.30pm, when many Australians were logging in to complete the census forms. According to the ABS, the situation was exacerbated by a “hardware failure when a router became overloaded” and a “false alarm in some of the system monitoring information.”

The result? The bureau closed down the online form.

The ABS stressed that this was not a hack and that no-one got access to the data that two million Australians had already submitted at the time of the incident. This was apparently confirmed by IBM (IBM) and the Australian Signals Directorate, which is the country’s equivalent to the NSA. Chief statistician David Kalisch claimed the attack came from overseas.

Although the census is supposed to capture a snapshot of the nation on August 9, Australians should still be able to submit their census forms in the coming weeks.

This year’s census was already hugely controversial, because the ABS had decided to store the gathered information for four years, rather than the traditional 18 months. This sparked a sizeable privacy debate, although the statisticians insisted that the longer retention period would allow them to make better use of the data.

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Several senators had refused to participate in the census due to the privacy issue, and the website’s closure gave the opposition an opportunity to bash the government for moving to online census forms this year.

Michael McCormack, the minister in charge of running the census, initially claimed there had been no attack at all, just an “attempt to frustrate” the census process. However, he clarified his words by saying “attacked” would have suggested the theft of information.

Kalisch said the router that had buckled belonged to the telecoms firm Telstra, but Telstra subsequently denied it had anything to do with it.

Whatever happened, it was hugely embarrassing and a salutary lesson about the dangers of online polling at this point in time.