Passing the _prefix_ here seems a bit out of place. I see you have made the prefix as part of the `FailTicket` and maybe could also add to `FailData` (or maybe the `f_ip` key in `addFailures` becomes `f_ip_prefix`?). You should be able to pass the _prefix_ value as part of the `FailTicket` in `FailManager.addFailures`, from both `Filter.processAndAddLine` and `Filter.addBannedIP`.. This also then avoids having to modify each backend.