ModSecurity is a plugin for Apache web servers which acts as a web app layer firewall. It is used to prevent attacks toward script-driven websites by employing security rules which contain particular expressions. This way, the firewall can prevent hacking and spamming attempts and preserve even websites which are not updated often. For instance, a number of failed login attempts to a script admin area or attempts to execute a specific file with the intention to get access to the script will trigger particular rules, so ModSecurity will block these activities the moment it identifies them. The firewall is extremely efficient since it screens the whole HTTP traffic to a website in real time without slowing it down, so it could prevent an attack before any harm is done. It additionally maintains an exceptionally comprehensive log of all attack attempts that includes more info than standard Apache logs, so you can later analyze the data and take additional measures to increase the security of your websites if needed.