ModSecurity is a plugin for Apache web servers that acts as a web application layer firewall. It is employed to prevent attacks towards script-driven websites through the use of security rules that contain particular expressions. In this way, the firewall can prevent hacking and spamming attempts and shield even websites that are not updated on a regular basis. For example, a number of failed login attempts to a script administrator area or attempts to execute a specific file with the objective to get access to the script shall trigger certain rules, so ModSecurity will block out these activities the moment it discovers them. The firewall is incredibly efficient since it tracks the whole HTTP traffic to a website in real time without slowing it down, so it will be able to stop an attack before any harm is done. It furthermore keeps a very detailed log of all attack attempts which includes more info than traditional Apache logs, so you can later check out the data and take further measures to improve the security of your websites if needed.