Eerily similar to our Black Widow. Time for some chemical warfare if the are anything like their American look-alikes.
They are indeed related to the black widow. Redbacks rarely leave their nest and you normally spot the nest before the spider. The females are larger and the most dangerous because their fangs are long enough to bite. About 6% of people have a serious reaction to them and need the antivenom, but there have been no deaths from them since the antivenom was developed in the 60's. Bites normally occur when people inadvertently put their hand in a nest - when I was about 14 a friend got bitten and he spent a week in hospital and nearly died. They said he had an unusual and severe allergic reaction.