5.2.2. Protect portmap With IPTables

To further restrict access to the portmap service, it is a good idea to add IPTables rules to the server and restrict access to specific networks.
Below are two example IPTables commands that allow TCP connections to the portmap service (listening on port 111) from the 192.168.0/24 network and from the localhost (which is necessary for the sgi_fam service used by Nautilus). All other packets are dropped.
 iptables -A INPUT -p tcp -s! --dport 111 -j DROP iptables -A INPUT -p tcp -s --dport 111 -j ACCEPT 
To similarly limit UDP traffic, use the following command.
 iptables -A INPUT -p udp -s! --dport 111 -j DROP 


Refer to Chapter 7, Firewalls for more information about implementing firewalls with IPTables commands.