PRE-TALLY ACTIONS:
My very first suggestion was to remove records with desired IPs from stats files. But now I see that those files has no IP stored in them. So I would suppose reconfiguring Apache and ProFTPd to not save records if remote IP matches a list of white-listed IPs, as I've never done anything of that kind, it should be verified. I'm almost sure, it can be done with Apache, but not sure about ProFTPd, and really doubt about Exim.
Another way to go it would be to make those services to store a destination IP in stats files. But in this case how would directadmin treat such modification. It's a really question to me.
POST-TALLY ACTIONS:
Or, you might want to scan all necessary service logs and decrease calculated values of bandwidth. In this case pre-tally actions are no more required. But how accurate would it be?
As I really do not see any practical values of checking all of these suppositions for me, I'd would do it only, if you hire me. Thus maybe somebody else is eager to share a ready-made solution for you.
Let's see who else has anything to add.
