Say G'Day to Latrodectus hasselti

The Redback spider is about as Aussie as they come. Instantly recognisable they should send a tingle of fear down your spine when you see one. They are one of Australia's deadly spiders and have an incredibly painful bite curtsey of their neurotoxic venom: Venom is produced by glands in the cephalothorax, expelled venom travels through paired ducts from the cephalothorax exiting through the tip of the spiders hollow fangs. The venom of the redback spider is thought to be similar to other Latrodectus spiders and contains a number of high molecular weight proteins. One of which, alpha-latrotoxin (a neurotoxin), is active in humans. In vertebrates alpha-latrotoxin produces its effect through destabilization of cell membranes and degranulation of nerve terminals resulting in the release of neuro-transmitters; its causes uncontrolled release of the neurotransmitters acetylcholine, norephedrine, and GABA. The release of these neurotransmitters leads to the clinical manifestations of envenoming.[11]
For first aid do not bandage the bite as this concentrated the venom which is less efective if you let it dilute in the blood, however you should apply iced water to the site and take painkillers to manage the symptoms (exotic pain) and seek medical attention. There is an antivenene.

The CSIRO recommend that

you destroy the spiders as you find them. Poke a stick into the retreat to squash or remove the spider, and destroy any egg sacs. Take care not to be bitten.

I particularly like the last bit of advice.