The fundamental principles discussed in the previous section should help us in developing a set of best practices for creating firewall rules. Some of these will seem obvious, while others will be less so:
- The principle of least privilege should apply to our firewall rules; many firewall rules are too permissive. When possible, avoid creating firewall rules that have any in the destination, or at least limit the port range. Take advantage of the fact that pfSense blocks all network traffic by default.
- Periodically check your firewall rules, and delete rules that are no longer relevant. For example, a subnet may have a printer that is shared with other subnets. A rule is created to grant access to the printer on those subnets. If the printer is subsequently decommissioned or moved, the firewall rules should be changed accordingly. In corporate environments...
