Let's talk about APF. APF — Advanced Policy Firewall — is a policy-based iptables firewall system that provides simple, powerful control over your day-to-day server security. It might seem intimidating to be faced with all of the features and configuration tools in APF, but this blog should put your fears to rest. APF is an iptables wrapper that works alongside iptables and extends its functionality. I personally don't use iptables wrappers, but I have a lot of experience with them, and I've seen that they do offer some additional features that streamline policy management. For example, by employing APF, you'll get several simple on/off toggles (set via configuration files) that make some complex iptables configurations available without extensive coding requirements. The flip-side of a wrapper's simplicity is that you aren't directly in control of the iptables commands, so if something breaks it might take longer to diagnose and repair. Before you add a wrapper like APF, be sure that you know what you are getting into. Here are a few points to consider: Make sure that what you're looking to use adds a feature you need but cannot easily incorporate with iptables on its own. You need to know how to effectively enable and disable the iptables wrapper (the correct way ... read the manual!), and you should always have a trusted failsafe iptables ruleset handy in the unfortunate event that something goes horribly wrong and you need to disable the wrapper. Learn about the basic configurations and rule changes you can apply via the command line. You'll need to…