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shorewall firewall and spam

Posted on 2006-11-02
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hi all,

my server is getting spammed out.  I was using iptables to block the spammers but it wasnt working.  So I added shorewall firewall on top of it.  Here's the deal.  In shorewall (v. 3.2.5), I can disable listening ports just fine and the services stop working.  Now, with the services working I have been checking my network connections (netstat -an) and checking my mail logs.  I would like to blacklist certain IP's.  So, I added the IP's to the blacklist file and nothing happens, the IP's are still connected.  Now, when I specify tcp and the port of the spammer it kicks them off for a split second and then the reconnect with a different port.  i.e.  smtp 25 listening on localhost, spammer connects to smtp but using some random port number.  If I block their ip and the random port number they get kicked off but come back with a different port number.

Basically I cannot block certain IP's successfully.  I tried setting up a sorbs.net rdns, but that stops remote users from connecting using pop3/smtp.

please help.
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Question by:newbe101
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jhughesco earned 1000 total points
ID: 17874767
You will not succeed with this method as the source of spam constantly changes, you simply can't keep up.  As more sources of spam become aware of your SMTP server, it will only get worse.

Check out this project and consider deploying: http://spamassassin.apache.org/

Now were talking about a spam filter, you'll get it under control.

-Jeff
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by:kblack05
kblack05 earned 1000 total points
ID: 17914924
Why not attenuate your server to only listen to SMTP requests from your own network block?
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by:kblack05
ID: 17914930
By the way, all shorewall does is put an interface on top of iptables, they are not different methods. Shorewall uses the same facilities as IPTables, it's just creating a nice interface to manage the rules.
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