If it was the Australian Medicare Statistics Reporting Service on June 18th it may have been part of this incident: https://collusion.wiki/ - the bulk of that coordinated activity was between 16th and 21st of June, and we know they were hitting UK government data sites.

I had a dig around in the data that they published on that site and found references to www.aihw.gov.au and viz.aihw.gov.au and vizprod.aihw.gov.au

https://collusion.wiki/explorer/label/ResearchHelperY

I think you're right. A bunch of aihw.gov.au references from this ResearchHelperY

Reporting says it wrote stuff to the server too, wondering what that is about.