ModSecurity is a plugin for Apache web servers that functions as a web application layer firewall. It is used to prevent attacks against script-driven sites through the use of security rules which contain particular expressions. This way, the firewall can prevent hacking and spamming attempts and shield even websites which aren't updated regularly. For example, numerous unsuccessful login attempts to a script administrative area or attempts to execute a specific file with the objective to get access to the script will trigger particular rules, so ModSecurity shall block these activities the moment it identifies them. The firewall is extremely efficient because it monitors the entire HTTP traffic to a site in real time without slowing it down, so it will be able to stop an attack before any harm is done. It furthermore keeps an exceptionally comprehensive log of all attack attempts that includes more information than typical Apache logs, so you can later analyze the data and take further measures to increase the security of your websites if required.