ModSecurity is a plugin for Apache web servers which functions as a web app layer firewall. It is used to stop attacks towards script-driven Internet sites by employing security rules that contain specific expressions. In this way, the firewall can block hacking and spamming attempts and shield even Internet sites that aren't updated regularly. For example, a number of unsuccessful login attempts to a script administrator area or attempts to execute a certain file with the objective to get access to the script shall trigger particular rules, so ModSecurity shall block out these activities the second it identifies them. The firewall is very efficient since it monitors the entire HTTP traffic to a site in real time without slowing it down, so it can easily stop an attack before any harm is done. It furthermore maintains a very detailed log of all attack attempts which features more information than traditional Apache logs, so you can later analyze the data and take additional measures to increase the security of your sites if necessary.