[SLUG] Detailed question about securing an small business Linux Server

From: JVergara@equinox.com
Date: Fri Jan 11 2002 - 10:51:40 EST


I have a question for the security gurus out there about setting up
security measures (using Ipchains or other methods) to close ports
against eventual break ins.

I am using a Linux RH 7.2 with two network cards - eth0 connects to
the internal network (192.162.0.) and the eth1 is connected via pppoe
to the Internet using ADSL. (so the IP address changes every time you
restart pppoe).

I am using the Linux server as internal pop server, smtp server
(using qmail) , samba server and ssh server.

When I run nmap -v in each interface, I get that the POP3 (110), smtp
(25), ssh(22), smb, sunrpc(111) are open in both interfaces.

How do I do it to close the ports POP3 and samba only for the external
interface (eth1 or ppp0 ?) or to deny incoming connections from the
internet?
Should I close the smtp port for the external interface too?

What do you need the sunrpc (111) port open for?

Do you know of a good tutorial to understand ipchain rules better?
RH 7.2 sets some rules to secure your server but I don't know if they
are good enough.

Thanks ,

Juan Vergara



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