bash脚本构建防火墙规则的实例

#!/bin/bash

# iptables script generated 2011-10-13
# http://www.mista.nu/iptables

IPT="/sbin/iptables"

# Flush old rules, old custom tables
$IPT --flush
$IPT --delete-chain

# Set default policies for all three default chains
$IPT -P INPUT DROP
$IPT -P FORWARD DROP
$IPT -P OUTPUT ACCEPT

# Enable free use of loopback interfaces
$IPT -A INPUT -i lo -j ACCEPT
$IPT -A OUTPUT -o lo -j ACCEPT

# All TCP sessions should begin with SYN
$IPT -A INPUT -p tcp ! --syn -m state --state NEW -s 0.0.0.0/0 -j DROP

# Accept inbound TCP packets
$IPT -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
$IPT -A INPUT -p tcp --dport 9922 -m state --state NEW -s 0.0.0.0/0 -j ACCEPT
$IPT -A INPUT -p tcp --dport 80 -m state --state NEW -s 0.0.0.0/0 -j ACCEPT
$IPT -A INPUT -p tcp --dport 443 -m state --state NEW -s 0.0.0.0/0 -j ACCEPT

# Accept inbound ICMP messages
$IPT -A INPUT -p ICMP --icmp-type 8 -s 0.0.0.0/0 -j ACCEPT

# Accept outbound packets
#$IPT -I OUTPUT 1 -m state --state RELATED,ESTABLISHED -j ACCEPT
#$IPT -A OUTPUT -p udp --dport 53 -m state --state NEW -j ACCEPT