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CAS-004 Practice Question: Is reviewing the configuration of a web…
A security engineer is reviewing the configuration of a web application firewall (WAF) that protects a public-facing e-commerce site. The site has been experiencing intermittent false positives that block legitimate customers during checkout. The WAF is deployed in blocking mode with a rule set that includes SQL injection and cross-site scripting (XSS) signatures. The engineer notices that legitimate credit card numbers containing the string 'OR' are being blocked. The site uses HTTPS and input validation on the server side. Which of the following actions would BEST resolve the false positives while maintaining security?
⚠ Common exam trap
CompTIA often tests the misconception that switching to detection mode or disabling the entire rule set is a safe compromise, but the correct approach is to surgically disable only the offending signature to balance security and usability.
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
✓
Disable the specific signature that matches the string 'OR' in the SQL injection rule set.
The false positive is caused by a specific SQL injection signature that matches the string 'OR' within legitimate credit card numbers. Disabling only that signature preserves the WAF's protection against actual SQL injection and XSS attacks while eliminating the false positive. The server-side input validation and HTTPS provide additional layers of defense, so removing the entire rule or switching to detection mode would unnecessarily weaken security.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Remove the WAF and rely on server-side input validation alone.
Why it's wrong here
Removing the WAF reduces defense-in-depth and removes a critical security layer.
- ✓
Disable the specific signature that matches the string 'OR' in the SQL injection rule set.
Why this is correct
This targets the exact cause of false positives while keeping other protections active.
- ✗
Change the WAF from blocking mode to detection mode.
Why it's wrong here
This would stop blocking all attacks, not just the false positives, weakening security.
- ✗
Add a custom rule to allow all traffic to the checkout page.
Why it's wrong here
This would bypass WAF protection entirely for the checkout page, exposing it to attacks.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.