1. Security PIN
2. Immutable storage

https://learn.microsoft.com/en-us/azure/security/fundamentals/backup-plan-to-protect-against-ransomware#azure-backup
Checks have been added to make sure only valid users can perform various operations. These include adding an extra layer of authentication. As part of adding an extra layer of authentication for critical operations, you're prompted to enter a security PIN before modifying online backups.

https://learn.microsoft.com/en-us/azure/security/fundamentals/backup-plan-to-protect-against-ransomware#steps-to-take-before-an-attack
Online immutable storage (such as Azure Blob) enables you to store business-critical data objects in a WORM (Write Once, Read Many) state. This state makes the data non-erasable and non-modifiable for a user-specified interval.