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 restricting access to specific networks.
Below is 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! 192.168.0.0/24 --dport 111 -j DROP
iptables -A INPUT -p tcp -s 127.0.0.1 --dport 111 -j ACCEPT
To similarly limit UDP traffic, use the following command.
iptables -A INPUT -p udp -s! 192.168.0.0/24 --dport 111 -j DROP