townx

Guys any iptables for ubuntu for just browsing and secures the various states like 1-7 as also stops service requests on established connections. Also do i need to make changes on sysctl for the iptables to work? in case of kernel panic how does this ipables handle it?

Hi,I have some problems about iptables rules under Ubuntu .
Is it necessary to create some script llike before to build the firewall,Will the rules got lost when I restart the server.

I create a simple firewall with the function of NAT,then restart the server.
type commands below in the terminal:
iptables -L -v

But display nothing.
And it seemd that the NAT function and the rules made last time are still available to use.

Hoping for your email.
Thanks.

For a personal home computer (running no services for the outside world), here is a simpler version :

#!/bin/bash
############################################################
#---- Script to setup a simple firewall using iptables -----
###
# * Blocks all incoming connections, except those opened by
# me, or related to already open connections
# * Blocks all forward requests
# * Allows all outgoing connections
###
############################################################

# Clearing all previous rules
iptables -F
# Setting Default Policies
iptables -P INPUT DROP
iptables -P OUTPUT ACCEPT
iptables -P FORWARD DROP
# Allowing already-established and related-incoming connections
iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT

Hi,
Great script - I've used it as the starter for my setup.

ShieldsUP notes that your script shows ports 0 and 1 as closed rather than in stealth mode, and also doesn't drop ICMP packets - meaning that if the machines are directly attached to the internet via ppp, or with an ADSL modem with no firewall, then they can be discovered.

Also your script doesn't handle dialup connections.

The following changes mitigates against these:

1. drop everything else on ppp
   iptables -A INPUT -i ppp+ -p udp -j DROP
   iptables -A INPUT -i ppp+ -p tcp -m tcp --syn -j DROP
   iptables -A INPUT -i ppp+ -p icmp -j DROP
2. Explcitly deal with port 0
   iptables -A INPUT -j DROP -p tcp --sport 0
   iptables -A INPUT -j DROP -p udp --sport 0
   iptables -A INPUT -j DROP -p tcp --dport 0
   iptables -A INPUT -j DROP -p udp --dport 0
3. Explcitly deal with port 1
   iptables -A INPUT -j DROP -p tcp --sport 1
   iptables -A INPUT -j DROP -p udp --sport 1
   iptables -A INPUT -j DROP -p tcp --dport 1
   iptables -A INPUT -j DROP -p udp --dport 1

regards

Colin

Greetings,

I would spell out everything I'm trying to do with IPtables but, to save time, I'll point you to the thread I started at http://ubuntuforums.org/showthread.php?t=337024

I've written my IPtables rules, saved them to a text file, and I'm now trying to install the rules I've written. I didn't think this portion of the process was going to be more difficult then actually learning IPtables, but go figure.

Anyway, I'm about to tear my hair out and would greatly appreciate your feedback.

Thank you for your time,

Nick

I'm new to all this so please bear with me! In your init script you use sudo to run the script, this is obviously necessary, but does that mean you've edited the sudoers file in order to launch that script without a pwassword?

For simple and effective firewall script try using Easy Firewall Generator
http://easyfwgen.morizot.net/gen/
It works as generator for you on end you simply have firewall.sh that you put where you want.
And you can always install it on your web server to have it locally so you can generate firewall.

Boris

Thank you for you iptables script. I have used your script every time I format my Linux machines. Its very handy. Its small and simple. I'm using pppoe connection so i have not created any links in initd but i call my firewall in my ppoe connection.

-TusharG

thanks!