ModSecurity is a plugin for Apache web servers which acts as a web app layer firewall. It is employed to prevent attacks against script-driven sites by using security rules which contain specific expressions. This way, the firewall can block hacking and spamming attempts and protect even Internet sites that are not updated regularly. For instance, numerous unsuccessful 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 specific rules, so ModSecurity will block out these activities the instant it identifies them. The firewall is extremely efficient because it monitors the whole HTTP traffic to an Internet site in real time without slowing it down, so it can stop an attack before any damage is done. It also maintains an incredibly thorough log of all attack attempts that features more information than conventional Apache logs, so you could later examine the data and take additional measures to increase the security of your sites if required.