ModSecurity is a plugin for Apache web servers that acts as a web application layer firewall. It is used to stop attacks toward script-driven sites by using security rules that contain particular expressions. This way, the firewall can block hacking and spamming attempts and shield even websites which aren't updated on a regular basis. For instance, numerous unsuccessful login attempts to a script administrative area or attempts to execute a certain file with the objective to get access to the script will trigger certain rules, so ModSecurity shall stop these activities the second it detects them. The firewall is extremely efficient since it tracks the entire HTTP traffic to a website in real time without slowing it down, so it can prevent an attack before any damage is done. It also keeps an exceptionally thorough log of all attack attempts which features more info than typical Apache logs, so you can later analyze the data and take further measures to improve the security of your sites if necessary.