Security+ Essentials is designed to provide the knowledge needed by IT professionals to pass the CompTIA Security+ exam. That said, the book is also of considerable use to anyone with a need to understand the concepts involved in creating and maintaining a secure IT environment.

Maximum Security: A Hacker's Guide to Protecting Your Internet Site and Network

Although this book cannot teach you everything you need to know, the references contained within this book can. Therefore, if you know very little about Internet security.