看板FB_security
标 题Re: quick FW question
发信站NCTU CSIE FreeBSD Server (Wed May 12 03:41:42 2004)
转信站ptt!FreeBSD.csie.NCTU!not-for-mail
In the immortal words of D J Hawkey Jr <
[email protected]>...
> Set up the mail server as the hub for your internal network, and have
> the workstations forward mail to it. If you're running sendmail on the
> workstations, put this in their .mc file:
> define(`SMART_HOST', `smtp:mailhub.privatedomain')
> And rebuild their sendmail.cf (I use the same .mc file for all U**X
> boxen on my network, except for the mail hub). Basically, just point
> all internal boxen's mailers to the hub.
I'm using Exim, and I already have this part working (smart host)
> My mail hub, in turn, defines SMART_HOST to be my ISP's mail cluster,
> and I define MASQUERADE_AS to be my ISP's domain (I use the feature
> masquerade_envelope, too). You might not be able to do this, of
> course, it'll depend on your connectivity.
Not really required for this particular setup.
> You'll need an MX record set up for the mail hub in your DNS.
Got one :)
> Given the above approach, the only thing I have in my firewall for
> SMTP is a rule for stateful outbound on ports 25 and 995 (I use SSL-
> enabled POP3 to download incoming mail from my ISP's mail cluster).
Hmmm, that doesn't really solve my problem, but it's useful to have in
the archives anyhow.
What I want to do is grab any outgoing packets bound for a port 25 and
redirect them back to the local mailserver which has spam/virus
filtering. This should eliminate problems of viruses/trojans which use
their own internal smtp servers to propogate themselves, coming from
this network.
The reason for this approach is the domain in question being RBL'd a
couple of days ago after one of the machines in this network had a
virus(actually a couple of thousand of various types).
Cheers
Tim
--
Tim Aslat <
[email protected]>
Spyderweb Consulting
http://www.spyderweb.com.au
Phone: +61 0401088479
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