Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Worthless

I purchased this book in hopes to have a reference guide for Iptables/Netfilter or even CheckPoint, but was sadly misled. The book covers only theory of how to build a firewall, while sighting no practical examples. It covers protocols, ports, and common types of security threats, but again gives no practical examples of how to write chains, tables or rules to prevent these attacks. If your a newbie to system administration you will learn quite a bit from this book, but if your a system admin such as I am looking for a reference guide THIS IS NOT IT