Data immutability and retention locking have gained enormous traction over the last many years owing to a severe surge in number of cyber and ransomware attacks. This presentation covers many aspects of data immutability and retention locking/WORM in the backup ecosystem. It talks about regulatory requirements for long term data retention, variants of retention locking, dual authorization model and role of security officer, various attributes of retention locking, integration of backup applications with retention locking, retention locking in replication and cloud storage.