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 small business is designing a defense-in-depth strategy for its e-commerce website. The web server is hosted in a cloud provider and handles credit card transactions. Which of the following additional controls best complements the existing firewall and IDS?
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
✓
Implement a web application firewall (WAF)
A web application firewall (WAF) adds a layer of protection against application-layer attacks, which complements the network-layer firewall and IDS. Antivirus is for endpoints, SIEM provides logging but not proactive defense, and load balancers distribute traffic but do not add security controls beyond resilience.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Set up a security information and event management (SIEM) system
Why it's wrong here
SIEM provides logging and analysis but is not a preventive control.
✗
Add a load balancer with SSL termination
Why it's wrong here
Load balancers improve availability and offload encryption, but do not provide security inspection.
✓
Implement a web application firewall (WAF)
Why this is correct
A WAF inspects HTTP/HTTPS traffic and blocks SQL injection, XSS, etc., adding a critical defense layer.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
Deploy a network-based antivirus on the web server
Why it's wrong here
Antivirus protects the server but does not address application-layer threats.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CAS-004 NAT questions on configuration and troubleshooting.
Security Architecture — This question tests Security Architecture — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Implement a web application firewall (WAF) — A web application firewall (WAF) adds a layer of protection against application-layer attacks, which complements the network-layer firewall and IDS. Antivirus is for endpoints, SIEM provides logging but not proactive defense, and load balancers distribute traffic but do not add security controls beyond resilience.
What should I do if I get this CAS-004 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CAS-004 NAT questions on configuration and troubleshooting.
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?
Static NAT maps one inside address to one outside address.
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