When the Customer-Specific Spam Submission is enabled and the backup of the SMG is restored, conduit_log shows the following errors every second after the restore. You want to know why and how to stop it.
Error from web server 403 - Forbidden : unable to GET: https://rules.ara.brightmail.com/some_number/rule_id_number
When the backup is more than 24-hour old, the submission rule gets stale and removed from the server. This causes the "403 Forbidden" errors.
Restore the backup within 24 hours to prevent these errors, or recreate and re-register a new Submitter ID, which will stop requesting the old rules.