Network Gateway Port Security

TL;DR

Only open the network ports you absolutely need on your gateway. Use a firewall to control access and regularly review open ports. Keep software updated to patch vulnerabilities.

1. Understand Your Network Needs

1. Identify Services: List all services running behind your gateway that require external access (e.g., web server, email server, VPN).
2. Port Mapping: Determine the specific ports each service uses. Common examples:
   • HTTP: Port 80
   • HTTPS: Port 443
   • SSH: Port 22
   • SMTP: Port 25
   • VPN (OpenVPN): Port 1194

2. Configure Your Firewall

Your gateway’s firewall is your primary defence. Most gateways have a built-in firewall; if not, consider installing one.

1. Default Deny: Set the firewall to block all incoming connections by default. This means nothing gets through unless you specifically allow it.
2. Allow Specific Ports: Create rules to allow traffic only on the ports identified in Step 1.

   # Example using iptables (Linux) - allow SSH from a specific IP address:
   iptables -A INPUT -p tcp --dport 22 -s 192.168.1.100 -j ACCEPT
   

3. Source IP Restrictions: Where possible, restrict access to these ports by source IP address. This limits who can connect.
   • For example, only allow SSH from your home or office IP address.
4. Destination IP/Port: Ensure the rules correctly specify the internal server’s IP address and port that should receive the traffic.

3. Port Forwarding (If Necessary)

If your gateway uses Network Address Translation (NAT), you may need to configure port forwarding.

1. Forward Only Required Ports: Configure port forwarding rules only for the ports identified in Step 1, directing traffic to the correct internal server.
2. Avoid Wildcard Forwarding: Never forward entire port ranges unless absolutely necessary. This significantly increases your security risk.

4. Disable Unnecessary Services

Turn off any services running on your gateway that you don’t need. Fewer services mean fewer potential attack vectors.

5. Regularly Review Firewall Rules

1. Scheduled Audits: Conduct regular audits of your firewall rules (at least quarterly) to ensure they are still appropriate and necessary.
2. Remove Obsolete Rules: Delete any rules that are no longer needed.
3. Log Monitoring: Enable firewall logging and review the logs for suspicious activity.

6. Keep Software Updated

Regularly update your gateway’s firmware and all software running on it to patch security vulnerabilities.

• Enable automatic updates if available.
• Check the manufacturer’s website for security advisories.

7. Consider Intrusion Detection/Prevention Systems (IDS/IPS)

For enhanced cyber security, consider implementing an IDS/IPS to detect and prevent malicious traffic.

8. Use Strong Passwords & Multi-Factor Authentication

Protect access to your gateway’s configuration interface with strong passwords and enable multi-factor authentication where possible.