Fired up on firewalls

So while we'll get round to better protecting services running on those ports we absolutely need, we can also create access controls using a basic firewall and, for that, let's consider two options:

• The first is the common-or-garden iptables solution, a packet filtering framework with which we manage rules from the command line

• The second is ConfigServer, the open source GUI that bundles its firewall with intrusion detection and analysis features and which, by chance, works nicely with Webmin

Bog-standard iptables firewall

This may be basic, but it works. Try a door and unless it's whitelisted, it won't budge.

The assumption here is that you either do not have a firewall, else that it needs re-addressing. For the former, we will install the package and, for both, we'll tune the ruleset.

Assume root privileges and list your current rules:

sudo -i
/sbin/iptables -L

If it looks like this, you have no rules:

Or if instead you receive an error like this, then the package isn't...