We have no laws that cover fax spam
Although Australia has a and a Spam Act which regulates unsolicited email and sms messages and a Do Not Call Register to which (private) fixed and mobile numbers can be added there is no legislation which covers unsolicited faxes at this stage.
At the time of writing, according to The Australian Communications and Media Authority’s website
The Government has recently announced its intention to expand the Do Not Call Register, to cover both business numbers and fax numbers. When this is implemented, it may reduce these types of calls being made where people register their numbers.