ModSecurity is a highly effective web app layer firewall for Apache web servers. It monitors the entire HTTP traffic to a website without affecting its functionality and when it identifies an intrusion attempt, it prevents it. The firewall also maintains a more comprehensive log for the traffic than any web server does, so you'll manage to keep an eye on what is going on with your sites a lot better than if you rely only on conventional logs. ModSecurity works with security rules based on which it stops attacks. For example, it identifies if someone is attempting to log in to the administrator area of a particular script several times or if a request is sent to execute a file with a certain command. In such situations these attempts set off the corresponding rules and the firewall software hinders the attempts immediately, and then records in-depth info about them within its logs. ModSecurity is one of the very best software firewalls on the market and it can protect your web applications against a huge number of threats and vulnerabilities, particularly if you don’t update them or their plugins regularly.