"Hello, this call is from the Investigation Division of Department of Home Affairs. The reason behind this call is that there is a legal case being filed under your name, as your identity is being used for several illegal activities. There is an arrest warrant issued under your name as well. To talk to a federal officer from the Department of Home Affairs, press "1" now..."

This is a computer generated voice. This is the 5th call exactly like this I have received in the last 2 weeks, with one call from a mobile and each subsequent call from a different number in Sydney.