Telstra has been forced to reset 35,000 passwords after its gaming website GameArena and online gaming shop were hacked.
Usernames, email addresses and encrypted passwords for the site were thought to be compromised.
Financial or credit card data was not stored on the third party-hosted sites.
Telstra was re-issuing new passwords to users and has warned customers to reset affected passwords that were re-used on other sites.
GameArena was developed by Brisbane-based Mammoth Media.