The answer is a next-generation firewall (NGFW) with intrusion prevention. This is the correct choice because an NGFW performs deep packet inspection at the application layer, allowing it to analyze the actual content of database queries and detect malicious SQL injection patterns, such as 'OR 1=1', that traditional port-based firewalls would miss. On the CompTIA SecurityX CAS-004 exam, this scenario tests your understanding of segmentation between tiers and the specific capabilities required for application-layer inspection; a common trap is choosing a web application firewall (WAF), but remember that a WAF protects inbound web traffic, whereas an NGFW with IPS is best for inspecting internal traffic between the application and database tiers. A useful memory tip: think of the NGFW as the "deep reader" between tiers—it reads the SQL, not just the packet headers.
CAS-004 Security Architecture Practice Question
This CAS-004 practice question tests your understanding of security architecture. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 architect is designing a segmentation strategy for a multi-tier web application. The public-facing web servers must communicate only with application servers, and application servers must communicate only with database servers. The architect wants to use a firewall that can inspect application-layer traffic to prevent SQL injection attacks. Which firewall type should be deployed between the application tier and the database tier?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Next-generation firewall (NGFW) with intrusion prevention
A next-generation firewall (NGFW) with intrusion prevention is the correct choice because it can perform deep packet inspection (DPI) at the application layer, allowing it to detect and block SQL injection payloads within database queries. Unlike simpler firewalls, an NGFW integrates signature-based and behavioral IPS engines that can identify malicious SQL patterns (e.g., 'OR 1=1') in traffic between the application and database tiers, providing the required application-layer inspection.
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.
✗
Packet filtering firewall
Why it's wrong here
Packet filtering only inspects headers, not application payloads, so it cannot detect SQL injection.
✓
Next-generation firewall (NGFW) with intrusion prevention
Why this is correct
NGFWs can perform deep packet inspection and use IPS signatures to detect SQL injection in database protocols.
Related concept
Read the scenario before looking for a memorised answer.
✗
Stateful firewall
Why it's wrong here
Stateful firewalls track connection state but do not inspect application-layer content.
✗
Web application firewall (WAF)
Why it's wrong here
WAFs inspect HTTP traffic; database traffic uses protocols like MS-SQL or MySQL, not HTTP.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the WAF's ability to inspect HTTP traffic with the need for application-layer inspection between application and database tiers, forgetting that database protocols (e.g., SQL) are not HTTP-based and require a different inspection engine like an NGFW with IPS.
Detailed technical explanation
How to think about this question
Under the hood, an NGFW with IPS uses protocol decoders to parse database protocols like MySQL, MSSQL, or Oracle TNS, applying signature patterns such as regex for SQL injection keywords (e.g., UNION, SELECT, DROP) and anomaly detection for query length or character encoding. In a real-world scenario, if the application server sends a crafted query like 'SELECT * FROM users WHERE id = 1; DROP TABLE users;', the NGFW's IPS can match this against known SQL injection signatures and drop the packet before it reaches the database, whereas a WAF would miss this because it operates on HTTP, not the raw SQL stream.
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 Architecture — This question tests Security Architecture — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Next-generation firewall (NGFW) with intrusion prevention — A next-generation firewall (NGFW) with intrusion prevention is the correct choice because it can perform deep packet inspection (DPI) at the application layer, allowing it to detect and block SQL injection payloads within database queries. Unlike simpler firewalls, an NGFW integrates signature-based and behavioral IPS engines that can identify malicious SQL patterns (e.g., 'OR 1=1') in traffic between the application and database tiers, providing the required application-layer inspection.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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