ModSecurity is a highly effective firewall for Apache web servers that is employed to prevent attacks against web apps. It tracks the HTTP traffic to a particular site in real time and prevents any intrusion attempts the moment it discovers 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 several times triggers one rule, sending a request to execute a certain file which may result in getting access to the Internet site triggers a different rule, etc. ModSecurity is amongst the best firewalls available and it'll secure even scripts which aren't updated on a regular basis as 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 much more specific than the standard logs provided by the Apache server, so you could later examine them and determine whether you need to take additional measures so as to improve the safety of your script-driven sites.
