iptables question

Hello
I recentrly installed Slackware Linux 10 into a box with static ip address (my first one, its hard here in greece to have dsl internet).

I have a problem with iptables:
I dont know how to tell iptables to block a specific port or port range to the world. Let me explain. This box runs ftp, mail and irc server. But I want these services to run only in the local network and any requests from the .."outside" to be blocked.
how can i achieve this?

Reading the documentation is really all you need:
http://www.netfilter.org/documentati...ing-HOWTO.html

Quote:

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to block a specific port or port range to the world.

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There is a Golden Rule when it comes to firewalls.
You dont block specific ranges. The golden rule is to BLOCK EVERYTHING and then just allow what you really need.

Cheers.