The correct actions are to enable AWS WAF rate-based rules and enable VPC Flow Logs to analyze traffic patterns. Rate-based rules automatically block IP addresses that exceed a specified request threshold, which directly mitigates DDoS attacks on an ALB by throttling excessive traffic while preserving access for legitimate users. VPC Flow Logs complement this by capturing IP traffic metadata, allowing the security team to identify attack sources and refine WAF rules. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of layered DDoS mitigation—combining application-layer controls (WAF) with network-layer visibility (Flow Logs). A common trap is choosing to scale the Auto Scaling group or add more instances, which does not stop the attack and only increases cost. Remember the mnemonic: “WAF blocks the flood, Flow Logs find the blood.”
DOP-C02 Incident and Event Response Practice Question
This DOP-C02 practice question tests your understanding of incident and event response. 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 is experiencing a DDoS attack on their web application hosted on Amazon EC2 behind an Application Load Balancer (ALB). The attack is causing high CPU utilization on the instances. The security team needs to mitigate the attack with minimal disruption to legitimate users. Which TWO actions should the team take? (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 AWS WAF rate-based rules to block excessive requests from specific IP addresses.
AWS WAF rate-based rules are designed to automatically block IP addresses that exceed a specified request rate, which directly mitigates DDoS attacks by limiting excessive traffic from specific sources. This approach minimizes disruption to legitimate users because it only blocks IPs that exceed the threshold, preserving access for normal traffic patterns.
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.
✓
Configure AWS WAF rate-based rules to block excessive requests from specific IP addresses.
Why this is correct
Rate-based rules can block IPs that exceed a threshold.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enable AWS Shield Advanced on the ALB for additional DDoS protection.
Why it's wrong here
Shield Advanced requires subscription and is not an immediate action.
✓
Enable VPC Flow Logs to analyze traffic patterns and identify the source of the attack.
Why this is correct
Flow logs help understand the attack and adjust WAF rules.
Related concept
Read the scenario before looking for a memorised answer.
✗
Scale up the EC2 instances by increasing their instance size.
Why it's wrong here
Scaling up may not mitigate the attack and could increase costs.
✗
Place an Amazon CloudFront distribution in front of the ALB to cache content.
Why it's wrong here
CloudFront can help but not a quick fix; it also requires DNS changes.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse AWS Shield Advanced as a direct mitigation for application-layer DDoS attacks, when it primarily protects against infrastructure-layer attacks (e.g., SYN floods) and requires WAF for application-layer control.
Detailed technical explanation
How to think about this question
AWS WAF rate-based rules use a token bucket algorithm to track request counts per IP address over a sliding window (e.g., 5 minutes). When the threshold is exceeded, the rule triggers a block action for that IP, effectively rate-limiting at the ALB level. In real-world scenarios, this is critical for mitigating HTTP flood attacks where attackers use distributed IPs but still generate high request rates per source.
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 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.
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.
Incident and Event Response — This question tests Incident and Event Response — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure AWS WAF rate-based rules to block excessive requests from specific IP addresses. — AWS WAF rate-based rules are designed to automatically block IP addresses that exceed a specified request rate, which directly mitigates DDoS attacks by limiting excessive traffic from specific sources. This approach minimizes disruption to legitimate users because it only blocks IPs that exceed the threshold, preserving access for normal traffic patterns.
What should I do if I get this DOP-C02 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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