[CentOS] Anyway to ensure SSH availability?
Ljubomir Ljubojevic
office at plnet.rs
Thu Jun 30 08:43:36 UTC 2011
Robert Heller wrote:
> If the machine is a public-facing smtp server, I would look first to see
> if you are getting the problem I was having. Maybe looking at the
> maillog to see if the volume of incoming mail is just overwhelming the
> system. In which case you need to do things to keep sendmail from
> running to many processes, either by throttling the connection rate and/or
> be using the accessdb to discard or reject connection from known problem
> networks.
>
Very simple solution is to implement Reverse DNS check. My Postfix mail
server refuses to accept any mail from FQDN without valid reverse DNS. I
(was?) also use graylisting and few other measures, but Reverse DNS
helped immensely in lowering SPAM that comes to my mailboxes. I would
say that reduction is some 70-80%.
Ljubomir
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