The correct answer is to disable the specific signature that matches the string 'OR' in the SQL injection rule set. This surgically targeted approach resolves the false positive without compromising the WAF’s overall security posture, because it leaves all other SQL injection and XSS signatures active to block genuine attacks. The false positive occurs because the WAF’s pattern-matching engine flags the substring 'OR' inside legitimate credit card numbers, not because the rule set itself is flawed. On the CompTIA SecurityX CAS-004 exam, this scenario tests your ability to perform granular WAF tuning rather than taking the blunt approach of disabling an entire rule or switching to detection mode—a common trap where candidates overcorrect and weaken defenses. Remember that server-side input validation and HTTPS remain as compensating controls, so a precise signature disable is both safe and effective. Memory tip: think “scalpel, not sledgehammer” when fixing WAF false positives.
CAS-004 Security Engineering Practice Question
This CAS-004 practice question tests your understanding of security engineering. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
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?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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.
Option B is correct because 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.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
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.
Detailed technical explanation
How to think about this question
WAF signatures often use pattern matching on decoded request bodies; the string 'OR' in a credit card number like '1234 5678 9012 3456' can match a SQL injection pattern designed to catch 'OR 1=1' attacks. Disabling a specific signature is a targeted tuning action that avoids the performance overhead of custom rules or the risk of detection mode. In real-world scenarios, false positives from credit card numbers are common because they contain sequences like 'OR' or 'AND' that overlap with SQL keywords.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Security Engineering — This question tests Security Engineering — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Disable the specific signature that matches the string 'OR' in the SQL injection rule set. — Option B is correct because 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.
What should I do if I get this CAS-004 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This CAS-004 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-004 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.