ModSecurity is an effective firewall for Apache web servers that is employed to stop attacks toward web apps. It tracks the HTTP traffic to a particular website in real time and blocks any intrusion attempts the instant it detects them. The firewall uses a set of rules to do this - as an illustration, attempting to log in to a script admin area without success several times triggers one rule, sending a request to execute a particular file which may result in getting access to the site triggers a different rule, and so on. ModSecurity is amongst the best firewalls available on the market and it'll secure even scripts which aren't updated often as it can prevent attackers from using known exploits and security holes. Quite detailed info about each intrusion attempt is recorded and the logs the firewall keeps are much more specific than the conventional logs provided by the Apache server, so you can later analyze them and determine if you need to take additional measures so as to increase the security of your script-driven sites.