hardMultiple Choice
CAS-004 Practice Question: A global e-commerce company processes payment…
A global e-commerce company processes payment card data and is required to comply with PCI DSS. During a quarterly vulnerability scan, the security team discovers that a web application firewall (WAF) rule is blocking legitimate traffic, causing transaction failures. The WAF is a critical compensating control for a known vulnerability in the application that cannot be patched for 90 days. The compliance officer is concerned about maintaining PCI DSS compliance while ensuring business continuity. The security team proposes temporarily disabling the WAF to restore service while they fine-tune the rules. Which of the following is the BEST action?
⚠ Common exam trap
The trap here is the false dichotomy between security and availability, leading candidates to choose extreme options like disabling the WAF or accepting failures, rather than seeking a balanced, temporary mitigation that preserves both.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Temporarily modify the WAF rule set to allow legitimate traffic while maintaining security, and schedule a permanent fix within 24 hours.
It balances the need for business continuity with the requirement to maintain the WAF as a compensating control for the unpatched vulnerability. By temporarily modifying the WAF rule set to allow legitimate traffic while still blocking malicious traffic, the team preserves the security control and avoids a compliance violation. Scheduling a permanent fix within 24 hours ensures the change is temporary and documented, aligning with PCI DSS change control and risk management requirements. This approach avoids the extremes of disabling the WAF entirely or allowing transaction failures.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Segment the affected application from the rest of the network and remove the WAF from the data path.
Why it's wrong here
Removing the WAF from the data path eliminates the compensating control PCI DSS requires for the unpatched vulnerability, leaving cardholder data exposed and non-compliant. Segmentation alone cannot substitute for the WAF's virtual patching. It tempts because isolating the application limits breach scope, which is valid when the vulnerability is patched or the control is genuinely redundant.
- ✗
Disable the WAF immediately to restore service and document the decision as a risk acceptance.
Why it's wrong here
Disabling the WAF removes the compensating control protecting an unpatched vulnerability, violating PCI DSS while leaving cardholder data exposed for 90 days. It tempts because restoring service quickly is urgent, and would be correct only if an equivalent control replaced the WAF's protection.
- ✗
Accept the risk of transaction failures and keep the WAF in place until the rules are fully tested.
Why it's wrong here
Keeping the WAF blocks legitimate transactions indefinitely, breaching the business-continuity requirement the stem sets alongside compliance. It tempts because preserving a compensating control protects PCI DSS compliance, and would be correct if transaction failures were tolerable while rules were tuned offline.
- ✓
Temporarily modify the WAF rule set to allow legitimate traffic while maintaining security, and schedule a permanent fix within 24 hours.
Why this is correct
Adjusting the WAF rule set preserves the compensating control PCI DSS requires for the unpatched vulnerability, restoring transaction flow without disabling protection entirely. A 24-hour remediation window keeps the exception tightly bounded, satisfying the standard's demand that compensating controls remain effective and documented throughout the 90-day patch deferral.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
This CAS-005 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CAS-005 exam.