They are large ferals. My whole family have are farmers and hunters all in nsw and we have almost all had at least one encounter with ferals the size of dogs. They are not just big they are very strong and aggressive, I have seen one kill a hunting dog.
We used to have one that would break through our flyscreen windows and come in our house at night, she would terrorise our house cats and if you turned on the lights and spooked her it would literally destroy the house... we eventually tamed her but she was really aggressive to other pets and would poo everywhere so we decided one day to take her for a "ride" (we couldnt kill her) she was so big we couldnt get her in a carrier we had to put her in the boot, we drove her over 30ks away to the town dump (plenty of food there) and popped the boot.......over night she walked back to our place, we had to put her down.