Getting Started with Apache ModSecurity on Debian and Ubuntu
ModSecurity is a Web Application Firewall: a program that can be used to inspect information as it passes through your web server, intercepting malicious requests before they are processed by your web application. This tutorial will show you how to install ModSecurity on Apache, and configure it with some sensible rules provided by the Open Web Application Security Project's Core Rule Set (OWASP CRS), which will help to protect your server against SQL injection, denial of service attacks, malformed requests, cross site scripting attacks, and more. And yes, you can use this guide with your Raspberry Pi if you're running Raspbian, Ubuntu, or another Debian derivative on it.