A large stockpile of usernames, email addresses and passwords has been posted online after popular aquarium site Cichlid-Forum.com was hacked.
The credentials included MD5-encrypted passwords which can be readily decrypted, and clear text emails and usernames.
Administrators had posted a notification on the site warning users of the hack.
"If you happen to use the same password for your email service provider that you used to register with Cichlid-Forum.com, we recommend you change that email account password as well," the announcement read.
The affected email domains were mainly linked to free online emal services but included 19 Australian government addresses including three from the Department of Defence, a Department of Foreign Affairs and Trade account, and an IT manager at the QLD Premier's office.
The use of such addresses was a concern because users may reuse their corporate passwords and offer hackers a way into their organisations' network.
The hackers' Twitter account SirLeaksALot has been disabled.