Not necessary to be afraid of Indonesia. Indonesia has no military the large number of soldiers they have is to keep peace in their own country.
The Indonesians would have to go to great expense to invade Australia and the north would be a dangerous place to be with nothing to take of military value and our air force pounding them.
Our armed forces have done numerous computer studies to demonstrate different scenarios if an attack occurred also Aussie companies service Indonesian war ships.
I don't think Australia has the slightest concern about security I think we would be more worried about China but then the Australian thinking is that Indonesia is a buffer against China.