ModSecurity is an efficient firewall for Apache web servers that is employed to prevent attacks against web applications. It monitors the HTTP traffic to a particular website in real time and prevents any intrusion attempts as soon as it detects them. The firewall uses a set of rules to do that - as an example, attempting to log in to a script admin area without success a few times sets off one rule, sending a request to execute a particular file which may result in accessing the site triggers a different rule, etcetera. ModSecurity is one of 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. Very detailed information about each and every intrusion attempt is recorded and the logs the firewall maintains are a lot more detailed than the conventional logs provided by the Apache server, so you could later examine them and determine if you need to take more measures in order to improve the security of your script-driven websites.