6 Mar
2005
6 Mar
'05
6:59 p.m.
On Sat, 5 Mar 2005, Eric Smith wrote:
I did away with my backup server. Spamming software
often seems to
ignore precedence, though I'm not sure whether that's deliberate or
sloppiness. But there's no easy way for my backup server to have a
list of valid email addresses on the primary, so the backup will accept
anything for the local domains. The backup kept falling over because
its queue was growing faster than it could process the entries.
The exploit is based upon the fact that the destination host
rejects unknown users; MX backups, not having that information,
generally accept *@domain, so the spammer hack is to find the
n>0th MX host, and queue it all up there. SPreads the load.
What we did was simply use virtusertable on the MX host to list
each and every single valid user. CLearly this doesn't scale for
many users but for the dozen or so we have it's fine.
/etc/mail/virtusertable also handles all the virtual domains etc
all i one place.