EFS-encrypted Files Were Detected (code 1624)

Situation

A file backup plan terminates with the following warning message: EFS-encrypted files were detected (code 1624). EFS-encrypted files were found in the backup source and were skipped. To back up EFS-encrypted files, a full backup is required

Cause

Some files in the backup source are EFS-encrypted, the Keep EFS encryption option is selected, and an incremental backup was attempted. The mechanism of backing up EFS-encrypted files 'as is' (encrypted) requires a full backup.

Solution

Force full backup.

1. Switch to the Backup Plans tab.
2. Find the plan that produced the warning, expand the plan execution control (the play button) and select Force Full Backup.

3. Continue with incremental backups.