In a chat room this morning, the group linked to AAPT's Wikipedia page, making that ISP the likely target. The group has also insisted, on Twitter, that the leak is not fake and that the ISP concerned knows what is happening.
Anonymous representatives have also said, in the same chat room, that the group's attack was not on AAPT itself but on a cold fusion server hosted at Melbourne IT. ZDnet reports that AAPT and Melbourne IT have both acknowledged the breach.
Anonymous has also, on its internet radio channel, articulated a raison d'être for the release, with a person identifying themselves as "Lorax" stating the release will serve as an example of how unsafe personal data will be under Australian Government's proposed data retention laws.
Chat has also suggested the group will release portions of data that in some way embarrass the Australian government.