iptables -P INPUT ACCEPT
iptables -F
iptables -A INPUT -i lo -j ACCEPT
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A INPUT -p tcp --dport 22 -j ACCEPT
iptables -P INPUT DROP
iptables -P FORWARD DROP
iptables -P OUTPUT ACCEPT
iptables -L -v

#!/bin/sh
IPTABLES=/sbin/iptables



# clear
$IPTABLES -F

# if pkg type is allow, then accept
#$IPTABLES -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT



# 如果同时在80端口的连接数大于10，就Drop掉这个ip

netstat -an | grep :80 | awk -F: '{ print $8 }' | sort | uniq -c | awk -F\  '$1>10 && $2!="" { print $2 }'  /etc/fw.list
less /etc/fw.list | sort | uniq -c | awk -F\  '$2!="" { print $2 }' > /etc/fw.list2
less /etc/fw.list2 > /etc/fw.list
while read line

    do
    t=`echo "$line"`
    $IPTABLES -A INPUT -p tcp -s $t -j DROP
done < /etc/fw.list2

# IP转发
$IPTABLES -A INPUT -p tcp --dport 20002 -j ACCEPT
$IPTABLES -A INPUT -d 172.16.204.7 -p tcp -m tcp --dport 20002 -i eth0 -j ACCEPT
$IPTABLES -t nat -A PREROUTING -d 211.100.39.44 -p tcp -m tcp --dport 20002 -j DNAT --to-destination 172.16.204.7:20002
$IPTABLES -t nat -A POSTROUTING -d 172.16.204.7 -p tcp -m tcp --dport 20002 -j SNAT --to-source 10.6.39.44


# if pkg visit 80,7710 port then accept
$IPTABLES -A INPUT -p tcp --dport 80 -j ACCEPT
$IPTABLES -A INPUT -p tcp --dport 8080 -j ACCEPT
$IPTABLES -A INPUT -p tcp --dport 22 -j ACCEPT
$IPTABLES -A INPUT -p tcp --dport 873 -j ACCEPT
# $IPTABLES -A INPUT -i eth0 -m limit --limit 1/sec --limit-burst 5 -j ACCEPT
$IPTABLES -A INPUT -p tcp --tcp-flags SYN,ACK,FIN,RST SYN -m limit --limit 30/m --limit-burst 2 -j ACCEPT
$IPTABLES -A FORWARD -p tcp --syn -m limit --limit 10/s -j ACCEPT
$IPTABLES -A FORWARD -f -m limit --limit 100/s --limit-burst 100 -j ACCEPT


# if pkg from allow ip then accept

$IPTABLES -A INPUT -p tcp -s 127.0.0.1  -j ACCEPT



# if pkg not above then deny

$IPTABLES -A INPUT -p tcp --syn -j DROP

下面这个防火墙测试结果更正确，能起到一定的防攻击的功能



#!/bin/sh

IPTABLES="/sbin/iptables"

echo "1" > /proc/sys/net/ipv4/ip_forward

$IPTABLES -P INPUT DROP
$IPTABLES -P FORWARD DROP
$IPTABLES -P OUTPUT DROP
$IPTABLES -F
$IPTABLES -X


$IPTABLES -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
$IPTABLES -A INPUT -p tcp --dport 22 -j ACCEPT
$IPTABLES -A INPUT -p tcp --dport 80 --tcp-flags SYN,ACK,FIN,RST SYN -m limit --limit 30/m --limit-burst 2 -j ACCEPT


$IPTABLES -A OUTPUT -p tcp -s 127.0.0.1 -j ACCEPT
$IPTABLES -A OUTPUT -p tcp -s 192.168.1.102 -j ACCEPT
$IPTABLES -A OUTPUT -p udp -s 127.0.0.1 -j ACCEPT
$IPTABLES -A OUTPUT -p udp -s 192.168.1.102 -j ACCEPT



$IPTABLES -A INPUT -p tcp --syn -j DROP