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2.2.2.2. 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. The first allows TCP connections to the port 111 (used by the portmap service) from the 192.168.0.0/24 network. The second allows TCP connections to the same port from the localhost. This 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

Note

Refer to Section 2.7, “Firewalls” for more information about implementing firewalls with iptables commands.