The correct measures are using AWS WAF to filter common web exploits and applying security groups as a virtual firewall. This combination directly implements defense in depth by layering protections at the application and network levels: AWS WAF inspects HTTP/HTTPS requests for SQL injection or cross-site scripting, while security groups control traffic at the instance level by allowing only specific ports and sources. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your understanding of layered security for web applications behind an ALB, often appearing as a multi-select question where distractors like placing instances in public subnets or allowing direct internet access bypass the defense-in-depth principle. A common trap is assuming a single layer—like only a security group—is sufficient, but the exam expects you to recognize that web application firewalls and host-based firewalls serve different threat vectors. Remember the mnemonic “WAF the web, SG the host” to recall that AWS WAF protects against application-layer exploits while security groups guard the network perimeter.
SAP-C02 Continuous Improvement for Existing Solutions Practice Question
This SAP-C02 practice question tests your understanding of continuous improvement for existing solutions. 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.
A company runs a web application on EC2 instances behind an ALB. They want to improve the security posture by implementing defense in depth. Which TWO measures should they implement? (Choose TWO.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure security groups to restrict traffic to only necessary ports.
Defense in depth includes multiple layers. AWS WAF protects against web exploits. Security groups act as a virtual firewall. Option A (WAF) and Option D (security groups) are correct. Option B (public subnets) is less secure. Option C (direct internet access) bypasses security. Option E (public S3) is not relevant.
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.
✗
Store static assets in a public S3 bucket.
Why it's wrong here
Public S3 buckets can be a security risk if misconfigured.
✗
Place EC2 instances in public subnets for easier management.
Why it's wrong here
Public subnets expose instances to more risk.
✗
Allow direct internet access to the EC2 instances.
Why it's wrong here
Direct internet access bypasses the ALB and reduces security.
✓
Configure security groups to restrict traffic to only necessary ports.
Why this is correct
Security groups act as a firewall for EC2 instances.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SAP-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Continuous Improvement for Existing Solutions — This question tests Continuous Improvement for Existing Solutions — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Configure security groups to restrict traffic to only necessary ports. — Defense in depth includes multiple layers. AWS WAF protects against web exploits. Security groups act as a virtual firewall. Option A (WAF) and Option D (security groups) are correct. Option B (public subnets) is less secure. Option C (direct internet access) bypasses security. Option E (public S3) is not relevant.
What should I do if I get this SAP-C02 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 SAP-C02 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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Question Discussion
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