Spam from NAT boxes

[Julian Elischer]

Cesar wrote:

> Hi,
>
>   I have some NAT boxes running FreeBSD, each of these boxes do NAT 
> for like 100+ people.
>   Almost everyday my IPs got blacklisted because of spam. I cant block 
> the smtp traffic going out became some people need it to send true 
> e-mails.
>   Are there any tool to detect/block those spams?
>
>   I tought in a program that receive the connection diverted/forwarded 
> by ipfw and then deliver it to SpamAssassin ...
>
>   I also have an e-mail server fully configurated with anti-spam, 
> anti-virus ... I tried forward to this e-mail server all my NAT box 
> tcp connections to port 25.
>
>   ipfw add fwd xx.xx.xx.xx,25 tcp from 192.168.0.0/24 to any 25
>
>   I got some matches in this rule when I try to send an email, but I 
> didnt get redirected to my email server.

our email server needs the same rule,  fwd 127.0.0.1 ...... so that the 
incoming packet is not rejected.

remember, fwd doesn't alter the packet, justr where it is sent..  
Without the extra rule your mail server
will say "why the heck did *I* get his packet?" and discard it.

>
>
>   Any ideas and/or sugestions?
>
>
> Thanks
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