Mastering Linux Security and Hardening - Second Edition

Hands-on lab for basic iptables usage

You'll complete this lab on your Ubuntu virtual machine. Follow these steps to get started:

1. Shut down your Ubuntu virtual machine and create a snapshot. After you boot it back up, look at your iptables rules, or lack thereof, by using the following command:

sudo iptables -L

2. Create the rules that you need for a basic firewall, allowing for Secure Shell access, DNS queries and zone transfers, and the proper types of ICMP. Deny everything else:

sudo iptables -A INPUT -m conntrack  --ctstate ESTABLISHED,RELATED  -j ACCEPTsudo iptables -A INPUT -p tcp --dport ssh -j ACCEPTsudo iptables -A INPUT -p tcp --dport 53 -j ACCEPTsudo iptables -A INPUT -p udp --dport 53 -j ACCEPTsudo iptables -A INPUT -m conntrack ...