Only those that attempt to arrive by sea without a visa. A great deal of debate regards this matter as contrary to UN Convention for Refugees. Some were kept in offshore camps for many years awaiting resettlement whilst costing the Australian government (tax payers) approx AUD400k p.a. p.p. Personally I though a very expensive solution and cruel. There was a deal on the table for Malaysia to accept those arriving by sea, but for reasons unknown to me rejected by Oz government.
As happens in the US and rarely mentioned, thousands arrive every year by aiy, then claim asylum, overstay visa for years etc With a population of approx 27 million we have around 60,000 staying illegally, including US citizens.