This book teaches ModSecurity from the beginning to anyone with basic Linux skills. It starts by focusing on introducing ModSecurity, and explaining the concept of ModSecurity rules and how to write them. Later, it looks at the performance of ModSecurity and what sort of impact ModSecurity has on the speed of your web application. This book is written for system administrators or anyone running an Apache web server who wants to learn how to secure that server. It assumes that you are familiar with using the Linux shell and command-line tools, but does its best to explain everything so that those who are not Linux experts can make full use of ModSecurity.