Optus will not be able to keep secret a Deloitte report it commissioned into the cause of a major 2022 cyberattack that released sensitive customer data, with the Federal Court dismissing an appeal brought by the telecommunications group.

The decision of the full court of the Federal Court means that information in the report will be given to Slater & Gordon, the law firm pursuing a class action against Optus alleging the company failed to protect its customers’ personal information.