Re: Filtering SPAM with Linux

[Rajeev Kumar <rajeev () rajeevnet com>]

Ivan,
  You need to setup a mail server on your proxy box which will collect 
all incoming mail at port 25 and then apply SPAM filter there.

One practical solution could be, install postfix 
(http://www.postfix.org) as a mailgateway, postfix has lots of anti-spam 
setup procedure and you can follow some nice websites/papers on this setup.
After your mail gateway, you can deliver mails to next hop (i.e your MS 
exchange server).
Look for this sites on how to setup postfix with antispam.

http://www.advosys.ca/papers/postfix-filtering.html
http://www.securitysage.com/guides/postfix_uce.html
http://jimsun.linxnet.com//misc/postfix-anti-UCE.txt
http://www.mengwong.com/misc/postfix-uce-guide.txt
http://www.postfix.org/uce.html


Also you can incorporate some third party spam filters such as 
Spamassassin (Open source).
Sophos Puremessage (Commercial , bit costly anti-spam filter but works 
very nicely)

Similar can be done with sendmail also, but I would prefer postfix which 
is lot better to administer than sendmail.

Hope this helps.

Rajeev

ivan.hernandez () globalsis com ar wrote:
> Hello. I have a box with linux that is acting as NAT and Firewall (also
> cache with squid and reverse proxy with pound).
> I have an internal MS Exchange server that goes to internet via NAT, and
> i dont have any chance of removing it, but i would like to filter the
> incoming traffic to remove spam.
> My net looks something like this:
>
>
> INTERNET <---> x.x.x.x LINUX BOX 10.1.20.100 <---> 10.1.20.1 MS Exchange
>
> What can i use in the linux box? I have found things like MessageWall and
> so, but i need better recomendations from people that already doed it.
>
> Thanks!!
> Ivan Hernandez
>
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any course! All of our class sizes are guaranteed to be 10 students or less 
to facilitate one-on-one interaction with one of our expert instructors. 
Attend a course taught by an expert instructor with years of in-the-field 
pen testing experience in our state of the art hacking lab. Master the skills 
of an Ethical Hacker to better assess the security of your organization. 
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