Firewall Testing Guide

TL;DR

This guide provides a step-by-step approach to testing your inhouse firewall’s effectiveness. It covers planning, tools, techniques (including port scanning, vulnerability scanning, and penetration testing), and reporting. Regular testing is crucial for maintaining strong cyber security.

1. Planning Your Firewall Test

1. Define Scope: What parts of the firewall will you test? Focus on critical assets and services first.
2. Set Objectives: What are you trying to achieve with this test? (e.g., identify open ports, verify rule effectiveness, assess response time).
3. Rules of Engagement: Document what is allowed and disallowed during the test. This prevents accidental disruption or legal issues. Get approval from relevant stakeholders.
4. Testing Environment: Ideally, use a separate testing environment that mirrors your production network. If not possible, schedule tests during off-peak hours.

2. Tools You’ll Need

• Nmap: A powerful port scanner for discovering open ports and services. (https://nmap.org/)
• Nessus: A vulnerability scanner to identify weaknesses in your systems. (Commercial, but has a free ‘Home’ version). (https://www.tenable.com/products/nessus)
• Metasploit: A penetration testing framework for simulating attacks. (Commercial, but has a free community edition). (https://www.metasploit.com/)
• Wireshark: A network protocol analyzer to capture and inspect traffic. (https://www.wireshark.org/)

3. Testing Techniques

1. Port Scanning (Nmap): Identify open ports on your firewall and internal systems.

   nmap -sV -p 1-65535 

   This command scans all TCP ports for common services.

2. Vulnerability Scanning (Nessus): Scan your firewall and internal systems for known vulnerabilities.
   Follow the Nessus setup guide to configure a scan policy that suits your needs.
3. Rule Verification: Test if your firewall rules are working as expected.
   • Attempt to access blocked services from both inside and outside the network.
   • Use Wireshark to verify traffic is being dropped or allowed according to your rules.
4. Penetration Testing (Metasploit): Simulate real-world attacks to identify weaknesses.
   • Start with information gathering and reconnaissance.
   • Attempt to exploit identified vulnerabilities using Metasploit modules.
   • Document all successful exploits and potential impact.
5. Traffic Analysis (Wireshark): Capture network traffic during testing to analyze firewall behavior.

   wireshark -i 

   Filter the captured traffic based on IP addresses, ports, or protocols.

4. Reporting Your Findings

1. Document Everything: Keep a detailed record of all tests performed, tools used, and results obtained.
2. Prioritize Vulnerabilities: Rank vulnerabilities based on severity (Critical, High, Medium, Low).
3. Provide Remediation Recommendations: Suggest specific steps to fix identified weaknesses.
   • Update firewall rules.
   • Patch vulnerable software.
   • Implement stronger security controls.
4. Share with Stakeholders: Present your findings and recommendations to relevant teams (e.g., IT, Security).

5. Ongoing Testing

Firewall testing should not be a one-time event. Regularly schedule tests (at least quarterly) to ensure continued cyber security effectiveness. Automate where possible.