Which practice is recommended for vulnerability testing in firewall management?

• A. It should be performed after changes
• B. It should be performed before changes
• C. It should be performed only during audits
• D. It should be optional

Answer: (A)

Testing vulnerabilities after applying firewall changes is essential because changes can introduce new weaknesses that wouldn’t exist in the previous configuration. When you implement new rules or adjust existing ones, there can be interactions between rules, unintended open ports, or misconfigurations that only become apparent once the changes are live. Running vulnerability testing at this point validates the actual security posture of the firewall, confirms that the changes achieve the intended access control, and helps catch issues before they can be exploited.

Testing before changes is helpful for planning and catching issues early, but it doesn’t reflect how the live system will behave after the changes take effect. Relying only on audits means gaps or drift introduced by recent changes might go unnoticed in between reviews, leaving opportunities for attackers. Making vulnerability testing optional reduces protection, since newly implemented configurations can hide vulnerabilities that post-change testing would reveal.