Firewall Rule Basics for Small Business Networks

A firewall controls which traffic can enter and leave your network. Most small business routers include a basic stateful firewall that automatically allows outbound traffic and blocks unsolicited inbound traffic. For more granular control, configure explicit rules. Firewall rules are processed in order — the first matching rule wins. Structure rules as: (1) allow specific trusted inbound traffic (e.g., your VPN port), (2) deny all other inbound traffic from the internet, (3) allow necessary outbound traffic, (4) log and deny everything else. An implicit 'deny all' at the end is a security best practice. For outbound rules, restrict what internal devices can connect to externally — for example, servers should only communicate on specific ports needed for their function. Regularly review firewall rules and remove rules that are no longer needed. Document every rule: who requested it, what it does, and when it expires. Enable firewall logging for denied traffic and review logs for patterns that indicate scanning or attack attempts.