Azure Backup users will now have immutable WORM storage for their backups when immutability is enabled and locked on a Recovery Services Vault. When immutability is enabled, it ensures that a Recovery Point, once created, cannot be deleted or have its retention period reduced before its intended expiry. Now, when immutability is locked, Azure Backup will also use WORM-enabled immutable storage to meet any compliance requirements. This feature is applicable to both existing and new vaults with locked immutability. It is currently in preview in limited regions. For more details, please refer: Concept of Immutable vault for Azure Backup - Azure Backup | Microsoft Learn