Mine

#!/bin/sh
IPTABLES="iptables"

cat /proc/net/ip_tables_names | while read table; do

$IPTABLES -t $table -L -n | while read c chain rest; do

if test "X$c" = "XChain" ; then
	$IPTABLES -t $table -F $chain
fi

done
	$IPTABLES -t $table -X
done

$IPTABLES -F INPUT
$IPTABLES -F FORWARD
$IPTABLES -F OUTPUT

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

$IPTABLES -A INPUT -p icmp -j DROP

$IPTABLES -A INPUT -i lo -j ACCEPT
$IPTABLES -A OUTPUT -o lo -j ACCEPT

$IPTABLES -A INPUT -p tcp ! --syn -m state --state NEW -j DROP
$IPTABLES -A FORWARD -p tcp ! --syn -m state --state NEW -j DROP
$IPTABLES -A OUTPUT -p tcp ! --syn -m state --state NEW -j DROP

$IPTABLES -A INPUT -p tcp --tcp-flags ALL ALL -j DROP
$IPTABLES -A INPUT -p tcp --tcp-flags ALL NONE -j DROP
$IPTABLES -A INPUT -p tcp --tcp-flags ALL FIN,URG,PSH -j DROP
$IPTABLES -A INPUT -p tcp --tcp-flags SYN,FIN SYN,FIN -j DROP
$IPTABLES -A INPUT -p tcp --tcp-flags SYN,RST SYN,RST -j DROP

$IPTABLES -A INPUT -s 0.0.0.0 -j DROP
$IPTABLES -A INPUT -d 255.255.255.255 -j DROP

$IPTABLES -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
$IPTABLES -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
$IPTABLES -A OUTPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

$IPTABLES -A FORWARD -i br0 -s $LAN -m state --state NEW -j ACCEPT

$IPTABLES -A OUTPUT -m state --state NEW -j ACCEPT

$IPTABLES -A INPUT -i br0 -p tcp -s $LAN --dports 80 -m state --state NEW -j ACCEPT

$IPTABLES -t nat -A POSTROUTING -o vlan1 -s $LAN -j MASQUERADE

$IPTABLES -t mangle -A POSTROUTING -p tcp --tcp-flags SYN,RST SYN -m tcpmss --mss 1421:65535 -j TCPMSS --clamp-mss-to-pmtu

$IPTABLES -A INPUT -j DROP
$IPTABLES -A FORWARD -j DROP
$IPTABLES -A OUTPUT -j DROP