With immutable vaults, Azure Backup provides you an option to ensure that recovery points that are once created cannot be deleted before their intended expiry time. Azure Backup does this by preventing any operations which could lead to loss of backup data. Hence, this helps you protect your backups against threats like ransomware attacks and malicious actors by disallowing operations such as deleting backups or reducing retention in backup policies.
Immutable vaults is now in preview in selected regions and will be available in other regions in the coming weeks.
Please refer to the documentation for more details.