At common law, a bank is under a strict duty to maintain secrecy and confidentiality about its customer's account. This confidentiality belongs to the customer, not the bank. The basis for the bank's duty of confidence is contractual, but the duty is not absolute and is qualified by statute and case law, including the Tournier case, in all common law jurisdictions.
Paul Latimer, Australia, 14 Penn St. Int'l L. Rev. 551 (1996).