ModSecurity is a plugin for Apache web servers that acts as a web app layer firewall. It's used to stop attacks toward script-driven websites by employing security rules that contain specific expressions. In this way, the firewall can stop hacking and spamming attempts and protect even Internet sites which are not updated regularly. For instance, several unsuccessful login attempts to a script administrative area or attempts to execute a certain file with the purpose to get access to the script will trigger certain rules, so ModSecurity will stop these activities the second it discovers them. The firewall is extremely efficient because it screens the entire HTTP traffic to an Internet site in real time without slowing it down, so it could stop an attack before any harm is done. It additionally maintains an incredibly thorough log of all attack attempts which contains more info than conventional Apache logs, so you could later analyze the data and take further measures to enhance the security of your websites if necessary.