Jim's organization has just completed a major Linux roll out and now all of the organization's systems are running the Linux 2.5 kernel. The roll out expenses has posed constraints on purchasing…

Jim's organization has just completed a major Linux roll out and now all of the organization's systems are running the Linux 2.5 kernel. The roll out expenses has posed constraints on purchasing other essential security equipment and software. The organization requires an option to control network traffic and also perform stateful inspection of traffic going into and out of the DMZ. Which built-in functionality of Linux can achieve this?