Your server’s security is a top priority. After all, you have undoubtedly spent a good deal of time and money acquiring, configuring, marketing, and optimizing your server. The moment it connects to the Internet, however, it has entered a hostile environment.
The first line of defense on any server is the network firewall. With it, you can block all but the most essential ports, restrict the type of port access users can have, and forward outside ports to different internal ones, all in an effort to thwart any attempts to gain unlawful access to the server.
The second line of defense consists of your software settings, making sure all software is up to date and all of your passwords are secure and rotated frequently.
Unfortunately, even if your software is secure and your firewall is tight, attackers can still find holes in your defenses, right where you have left them. It is like the dilemma of having windows in your house. They are necessary, but they leave you vulnerable. Likewise, you have to leave certain ports open so that your websites and web applications can access the Web. In turn, the Web can also access your server.
ModSecurity is an application firewall that adds another layer to your defense lines, protecting your server from one of its own weakest points: web applications. In the days of static websites, this was not so much of an issue, but with scripting languages like PHP that are used to create dynamic websites, attackers are constantly looking for ways to use those scripts against you and exploit your server.
An application firewall interacts with Apache, restricting what powers a web application actually has, effectively locking out attackers, even if they do manage to find a weakness in one of your scripts. Best of all, ModSecurity is free and open source. It is also easy to download and install, and the large user community provides additional rules and configuration help so that you can customize it to meet your server’s needs.