Here's [the PM's press conference transcript](https://www.pm.gov.au/media/press-conference-new-york) that revealed this incident:

JOURNALIST: Could you just clarify, did our security agencies completely miss this breach? We only found out once the company actually told us the breach?

PRIME MINISTER: Well, to be very clear, the way that this occurred was not in a way that would likely – I mean, this is not a security website where there is – this is a Medicare statistics portal.

This seems rather revealing. A pity journalists didn't ask about what protections were bypassed on the data that was obtained.