NetApp SnapLock is the designated technology for creating immutable, WORM (Write Once, Read Many) data copies. In Compliance mode, it ensures that once data is written and a retention period is set, it cannot be altered or deleted by anyone, including administrators, until that period expires. This feature is fundamental to a cyber vault's design, as it protects backup data from being encrypted, modified, or deleted by a ransomware attack, guaranteeing a clean, unalterable recovery point.

A. FlexCache volumes is a technology for caching frequently accessed data at remote sites to improve read performance; it does not provide immutability.

C. Volume Encryption provides data-at-rest security by encrypting data blocks, but it does not prevent authorized users or attackers from modifying or deleting the data.

D. Cloud Sync is a data mobility service for synchronizing data between on-premises ONTAP and cloud object stores, not for creating immutable on-premises copies.

- NetApp, Inc. (2022). TR-4814: NetApp Solution for Ransomware. Section: "Immutable Snapshot copies with SnapLock," Page 11. This document states, "SnapLock creates immutable copies of Snapshot backups that cannot be altered or deleted."

- NetApp, Inc. (2023). TR-4526: SnapLock Technology. Section: "SnapLock modes of operation," Page 6. This report details how SnapLock Compliance mode provides the strictest level of WORM protection.