Tax - Claiming a Capital Loss, page-5

A helpful link to the ATO website for your query. Google can be your friend and a useful tool, hotcopper is full of information that is generally not useful.

a key takeaway point I would like to mention, is the ~1 to 2800 dilution shareholders were savagely hit with is enough, in my opinion, to strip your current shares of value and should trigger a capital loss.

I am not a tax professional and you can read the ATO website yourself.