[CentOS] Security help desperately needed - more info

[mouss]

Anne Wilson wrote:
> /etc/hosts is fine.  All possible connections on the lan are correctly 
> defined.  dns resolution is via my isp, and again the IP addresses are 
> correctly set.  That leaves the security settings, where I believe the 
> problem is.  So, let's start with iptables.  I've never worked directly with 
> iptables before.  I use shorewall when I set up the older server, a long time 
> ago.  /usr/share/doc/iptables... doesn't help.  Does that mean that the man 
> pages are the only help?  Googling, I suppose.  Any particular documents 
> recommended?
>   

do an
# iptables-save > somefile

edit somefile and put the following 4 lines "somewhere" (before the 
lines that reject everything)

-A RH-Firewall-1-INPUT -p udp -m udp -s 192.168.0.0/24 --dport 137 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp -m udp -s 192.168.0.0/24 --dport 138 -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp -s 
192.168.0.0/24 --dport 139 -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp -s 
192.168.0.0/24 --dport 445 -j ACCEPT

adjust the IP sources (the -s 192.168.0.0/24) as you need. I am assuming 
that you have a rule like this:
-A  RH-Firewall-1-INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT


then
# iptables-restore < somefile

if you're happy with that, then
# iptables-save > /etc/sysconfig/iptables
so that this survives a reboot.