Secure iptables firewall configuration (only activate SSH,WEB,DNS service)

Iptables-F clear all rule chains iptables-X remove specific manual chain iptables-Z emptying counter iptables-P INPUT DROP / / default INPUT rules discard iptables-P OUTPUT DROP / / default OUTPUT rules discard iptables-P FORWARD DROP / / default FORWARD rules discard iptables-An INPUT-d 192.168.10.250-p tcp-m tcp-dport 22-j ACCEPT / / open SSH service inbound port iptables-An INPUT-d 192. 168.10.250-p tcp-m tcp-- dport 80-j ACCEPT / / Open WEB service inbound port iptables-An INPUT-s 127.0.0.1-d 127.0.0.1-j ACCEPT / / allow local loopback data iptables-An INPUT-p udp-m udp-sport 53-j ACCEPT / / packets from remote DNS server port 53 go through iptables-An INPUT-p udp-m udp-dport 53-j ACCEPT / / Packets entering port 53 of the local server can enter the local server through iptables-An INPUT-d 192.168.10.250-p icmp-j ACCEPT / / ICPM packets can enter the local server iptables-An OUTPUT-s 192.168.10.250-p tcp-m tcp-sport 22-m state-- state ESTABLISHED-j ACCEPT / / An OUTPUT-s 192.168.10.250-p tcp- M tcp-- sport 80-m state-- state ESTABLISHED-j ACCEPT / / Open outbound port iptables-An OUTPUT-s 127.0.0.1-d 127.0.0.1-j ACCEPT / / allow local loopback data iptables-An OUTPUT-p udp-m udp-sport 53-j ACCEPT / / packets outbound from local port 53 outbound via iptables-An OUTPUT-p udp-m udp-- dport 53- J ACCEPT / / packets outbound to remote DNS server port 53 via iptables-An OUTPUT-s 192.168.10.250-p icmp-j ACCEPT / / A pair of ICMP packets echo (ping command echo packet) service iptables save / / Save configuration information service iptables start / / turn on firewall service