Summary

As we mentioned in the previous chapter, a firewall alone might not be enough to secure your systems. We highly recommend the tools mentioned here for both the firewall and any Linux-based servers you have in your internal network or DMZs. A combination of Network and Host-based Intrusion Detection systems and kernel hardening (we cannot recommend grsecurity enough) can assist you in dramatically increasing the overall security posture of your network. If anything, this chapter should serve as a good basic checklist for any Linux-based server, or even desktop, you are using in your enterprise.

Aside from constructing good firewall rules, you will also need to secure the firewall itself to truly benefit from any increase in protection your firewall might be able to convey. If your firewall is vulnerable, then everything else that depends on it is equally vulnerable. Ensure that your firewall is the most secured system in your enterprise before focusing your efforts on anything else. As it is, in most enterprises, the firewall is the single most important and relied upon component in the security model. Even if your enterprise is different, always make sure your firewall's security posture sets the standard for everything else in your enterprise.