The operating system must implement cryptographic mechanisms to prevent unauthorized modification of all information at rest on organization-defined information system components. FileVault Disk Encryption must be enabled. This ensures that any data stored on the hard drive will be protected by cryptographic means when the system is powered off, mitigating the risk of unauthorized modification of that data. Selection of a cryptographic mechanism is based on the need to protect the integrity of organizational information. The strength of the mechanism is commensurate with the security category and/or classification of the information. Organizations have the flexibility to either encrypt all information on storage devices (i.e., full disk encryption) or encrypt specific data structures (e.g., files, records, or fields).