ModSecurity is a plugin for Apache web servers that functions as a web application layer firewall. It is employed to stop attacks against script-driven sites by employing security rules that contain specific expressions. This way, the firewall can stop hacking and spamming attempts and shield even sites which aren't updated regularly. For example, multiple failed login attempts to a script administrator area or attempts to execute a certain file with the purpose to get access to the script shall trigger specific rules, so ModSecurity will stop these activities the moment it identifies them. The firewall is quite efficient since it tracks the entire HTTP traffic to a website in real time without slowing it down, so it could prevent an attack before any damage is done. It additionally maintains a very detailed log of all attack attempts that contains more information than typical Apache logs, so you could later analyze the data and take additional measures to increase the security of your Internet sites if necessary.