The correct answer is to enable Azure Web Application Firewall (WAF) on Azure Front Door or Application Gateway. This is because WAF operates at the application layer (Layer 7), where it can inspect incoming HTTP traffic and block malicious payloads like SQL injection and cross-site scripting (XSS) by matching them against OWASP Top 10 rule sets. On the Microsoft Cybersecurity Architect exam, this question tests your ability to distinguish between network-layer and application-layer security controls—a common trap is confusing WAF with NSGs, which only filter IPs and ports, or with DDoS protection, which handles volumetric attacks. Remember that WAF is your dedicated shield for web application vulnerabilities, while Key Vault manages secrets, not traffic. A useful memory tip: think of WAF as the "bouncer" at the app's front door, checking every request for malicious code before it reaches your code.
SC-100 Practice Question: Design security solutions for applications and data
This SC-100 practice question tests your understanding of design security solutions for applications and data. 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.
Your team develops a web application hosted on Azure App Service. You need to secure the application against common web vulnerabilities like SQL injection and cross-site scripting. What should you implement?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Enable Azure Web Application Firewall (WAF) on Azure Front Door or Application Gateway.
Option C is correct because Azure Web Application Firewall (WAF) on Azure Front Door or Application Gateway protects against OWASP Top 10 threats including SQL injection and XSS. Option A is wrong because NSGs protect network traffic, not application layer. Option B is wrong because Key Vault is for secrets. Option D is wrong because DDoS protection is for network layer attacks.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Enable Azure Web Application Firewall (WAF) on Azure Front Door or Application Gateway.
Why this is correct
WAF protects against SQL injection, XSS, and other web threats.
Store application secrets in Azure Key Vault and enable managed identity.
Why it's wrong here
Key Vault protects secrets, not application vulnerabilities.
✗
Configure Network Security Groups (NSGs) on the App Service subnet to restrict inbound traffic.
Why it's wrong here
NSGs are network layer, not application layer.
✗
Enable Azure DDoS Protection on the virtual network.
Why it's wrong here
DDoS protects against volumetric attacks, not application vulnerabilities.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
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 block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SC-100 subnetting questions on CIDR, address ranges, and subnet selection.
Design security solutions for applications and data — This question tests Design security solutions for applications and data — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Enable Azure Web Application Firewall (WAF) on Azure Front Door or Application Gateway. — Option C is correct because Azure Web Application Firewall (WAF) on Azure Front Door or Application Gateway protects against OWASP Top 10 threats including SQL injection and XSS. Option A is wrong because NSGs protect network traffic, not application layer. Option B is wrong because Key Vault is for secrets. Option D is wrong because DDoS protection is for network layer attacks.
What should I do if I get this SC-100 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SC-100 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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