Understanding and building security rules

We now need to build some security rules to allow or deny traffic in and out of the network. The default rules will only allow intrazone traffic and will block everything else, as you can see here:

Figure 3.23 – Default security rules

We will first make sure "bad" traffic is dropped by creating two new rules—one for inbound and one for outbound traffic.

Dropping "bad" traffic

The inbound rule will have the external zone as a source and the three External Dynamic Lists (EDLs) containing known malicious addresses. These lists are updated via the threat prevention dynamic updates. The Source tab should look similar to the following:

Figure 3.24 – Reconfigured external dynamic lists

In the Destination tab, set the destination zones to both the external zone and any zone where you intend to host internal servers that you will allow inbound NAT to (for...