Which of the following backup procedures would only copy files that have changed since the last backup was made?

An incremental backup copies only the data that has been created or changed since the last backup activity was conducted, whether that last backup was a full or another incremental backup. This method is fast and requires the least amount of storage space compared to full or differential backups. For a full restoration, the last full backup and all subsequent incremental backups up to the point of recovery are required.

B. A differential backup copies all files that have changed since the last full backup, not the last backup of any type.
C. A daily backup describes a backup schedule or frequency, not the technical method used to select which files to copy.
D. A full backup copies all selected data regardless of when it was last modified or backed up.

1. National Institute of Standards and Technology (NIST). (2010). Special Publication 800-34 Rev. 1, Contingency Planning Guide for Federal Information Systems. Appendix G-3. It defines an incremental backup as one that processes "files that are new or changed since the last backup."

2. ISACA. (2019). CISA Review Manual, 27th Edition. Domain 4: Information Systems Operations and Business Resilience. Section 4.6.3 Backup and Restoration. This section details backup strategies, defining incremental backups as capturing data changed since the last backup.

3. University of California, Berkeley. Information Security Office. bSecure - Data Backup Options. The documentation distinguishes between backup types, stating, "An incremental backup stores all files that have changed since the last full, differential, OR incremental backup."