iptables script for you Gurus out there...
 

I haven't used iptables in quite some time now and just made an iptables script. This script was designed for a home network. Is there anything else I can do to beef up this script? I've spent a lot of time reading about iptables ( seems to be an endless journey ). Any thoughts would be appreciated.

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# iptables v1.2.10 #
# Firewall script to keep those unwanted attackers out of #
# my box... hopefully! #
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# Make default policies...

iptables -P INPUT DROP
iptables -P OUTPUT ACCEPT
iptables -P FORWARD DROP

# Allow loopback...

iptables -A INPUT -i lo -j ACCEPT

# Allow UDP port 53...

iptables -A INPUT -i eth0 -p udp --sport 53 -s 192.168.0.1/255.255.255.0 -m state --state ESTABLISHED,RELATED -j ACCEPT

# Add some TCP INPUT rules...

iptables -A INPUT -i eth0 -s 192.168.0.101/255.255.255.0 -d 0/0 -j ACCEPT
iptables -A INPUT -i eth0 -p tcp -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A INPUT -i eth0 -p tcp -s 0/0 -d 0/0 --dport 22 -j ACCEPT

# Drop those nasty packets...

iptables -A INPUT -i eth0 -p ALL -m state --state INVALID -j DROP
iptables -A INPUT -i eth0 -p tcp --tcp-flags ALL FIN,URG,PSH -j DROP
iptables -A INPUT -i eth0 -p tcp --tcp-flags ALL ALL -j DROP
iptables -A INPUT -i eth0 -p tcp --tcp-flags ALL SYN,RST,ACK,FIN,URG -j DROP
iptables -A INPUT -i eth0 -p tcp --tcp-flags ALL NONE -j DROP
iptables -A INPUT -i eth0 -p tcp --tcp-flags SYN,RST SYN,RST -j DROP
iptables -A INPUT -i eth0 -p tcp --tcp-flags SYN,FIN SYN,FIN -j DROP

I am no IPTables expert, but I have been reading a lot lately on the subject in prepartion for numerous projects.

i would ask the following;

Do you have any hosts behind this box that need to go outbound?

I see you are accepting SSH connection. I would say, if you can, put the Source IP from the ssh originating connection, if possible. That would give you more protection.

Personally, I would drop the bad stuff before I started accepting anything. I know that means more rules to traverse, but the way you've got it written, the nasty packet rules aren't doing anything since there are no ACCEPT rules after them.

Thanks for the input! This is what I have now...



#!/bin/bash

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# iptables v1.2.10 #
# Firewall script to keep those unwanted attackers out of #
# my box... hopefully! #
#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=




# Flush any existing rules...

iptables -F

# Make default policies...

iptables -P INPUT DROP
iptables -P OUTPUT ACCEPT
iptables -P FORWARD DROP

# Drop those nasty packets...

iptables -A INPUT -i eth0 -p ALL -m state --state INVALID -j DROP
iptables -A INPUT -i eth0 -p tcp --tcp-flags ALL FIN,URG,PSH -j DROP
iptables -A INPUT -i eth0 -p tcp --tcp-flags ALL ALL -j DROP
iptables -A INPUT -i eth0 -p tcp --tcp-flags ALL SYN,RST,ACK,FIN,URG -j DROP
iptables -A INPUT -i eth0 -p tcp --tcp-flags ALL NONE -j DROP
iptables -A INPUT -i eth0 -p tcp --tcp-flags SYN,RST SYN,RST -j DROP
iptables -A INPUT -i eth0 -p tcp --tcp-flags SYN,FIN SYN,FIN -j DROP

# Allow loopback...

iptables -A INPUT -i lo -j ACCEPT

# Allow UDP port 68...

iptables -A INPUT -i eth0 -p udp --sport 68 -s 192.168.0.1/255.255.255.0 -m state --state ESTABLISHED,RELATED -j ACCEPT

# Add some TCP INPUT rules...

iptables -A INPUT -i eth0 -s 192.168.0.101/255.255.255.0 -d 0/0 -j ACCEPT
iptables -A INPUT -i eth0 -p tcp -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A INPUT -i eth0 -p tcp -s 0/0 -d 0/0 --dport 22 -j ACCEPT

# Log DROPed packets...

#iptables -A INPUT LOG
#iptables -A INPUT DROP