The answer is to deploy Azure Application Gateway with Web Application Firewall (WAF) in front of the App Service. This combination directly meets all requirements because the WAF protects against common web vulnerabilities like SQL injection and cross-site scripting (XSS), while the Application Gateway handles TLS termination for encrypted traffic and provides native autoscaling to match demand, all within a single, cost-effective managed service. On the Microsoft Cybersecurity Architect exam, this scenario tests your ability to distinguish between Azure’s web protection services—specifically, knowing that Application Gateway WAF is the right fit for regional, single-region applications, whereas Azure Front Door is designed for global, multi-region deployments and carries higher cost. A common trap is choosing Azure Firewall, which operates at the network layer and does not inspect application-layer payloads. Remember the memory tip: “WAF on Gateway for regional, WAF on Front Door for global.”
SC-100 Design security solutions for infrastructure Practice Question
This SC-100 practice question tests your understanding of design security solutions for infrastructure. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
You are designing a security solution for a small business that uses Azure App Services to host a web application. The business has the following requirements: - The web application must be protected against common web vulnerabilities like SQL injection and cross-site scripting (XSS). - All traffic to the application must be encrypted. - The solution should be cost-effective and require minimal management overhead. - The application must be able to scale automatically based on demand. Which Azure service should you use to meet these requirements?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Deploy Azure Application Gateway with Web Application Firewall (WAF) in front of the App Service.
Option A is correct: Azure Web Application Firewall (WAF) on Application Gateway protects against web vulnerabilities, provides TLS termination, and supports autoscaling. Option B is incorrect: Azure Front Door also provides WAF but is more expensive and suited for global scenarios. Option C is incorrect: Azure CDN does not include WAF. Option D is incorrect: Azure Firewall is a network firewall, not a web application firewall.
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.
✗
Use Azure Firewall to inspect traffic to the App Service.
Deploy Azure Application Gateway with Web Application Firewall (WAF) in front of the App Service.
Why this is correct
WAF protects against common web attacks, provides TLS, and autoscales.
Related concept
Static NAT maps one inside address to one outside address.
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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this SC-100 question in full detail.
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 SC-100 NAT questions on configuration and troubleshooting.
Design security solutions for infrastructure — This question tests Design security solutions for infrastructure — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Deploy Azure Application Gateway with Web Application Firewall (WAF) in front of the App Service. — Option A is correct: Azure Web Application Firewall (WAF) on Application Gateway protects against web vulnerabilities, provides TLS termination, and supports autoscaling. Option B is incorrect: Azure Front Door also provides WAF but is more expensive and suited for global scenarios. Option C is incorrect: Azure CDN does not include WAF. Option D is incorrect: Azure Firewall is a network firewall, not a web application firewall.
What should I do if I get this SC-100 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 SC-100 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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