After having installed and configured FileAudit, the incremental Backup size of my server has increased.

Changing the NTFS permissions or NTFS audit settings resets the archive bit. As FileAudit modifies the Audit settings when defining the paths to audit, it will reset the archive bit once. It is therefore normal to have an increased backup size just after setting a folder path tree to audit.

But it will happen only once, just after the paths are defined on FileAudit and its NTFS Audit settings are configured. Once the folder paths are backed up, the backup software normally clears the archive bit. As FileAudit doesn’t modify again the Audit settings (except if you request it), the backup will come back to its regular size on the next iteration.