ModSecurity is a powerful firewall for Apache web servers which is employed to stop attacks towards web apps. It monitors the HTTP traffic to a particular site in real time and prevents any intrusion attempts the instant it identifies them. The firewall uses a set of rules to accomplish that - as an example, attempting to log in to a script administrator area without success many times sets off one rule, sending a request to execute a certain file that may result in accessing the Internet site triggers a different rule, etcetera. ModSecurity is among the best firewalls available on the market and it will preserve even scripts that are not updated on a regular basis since it can prevent attackers from employing known exploits and security holes. Quite thorough info about every single intrusion attempt is recorded and the logs the firewall maintains are considerably more specific than the standard logs created by the Apache server, so you could later take a look at them and determine whether you need to take extra measures in order to enhance the security of your script-driven sites.