- A
Configure Amazon CloudFront to block the IP address.
Why wrong: CloudFront can block IPs, but it's an additional layer not directly on the ALB.
- B
Modify the network ACL for the ALB's subnet to deny the IP address.
Why wrong: NACLs apply at subnet level, but ALBs operate at layer 7; NACL may not block if traffic goes through other paths.
- C
Use AWS WAF to create an IP set rule that blocks the IP address.
AWS WAF integrates with ALB to filter requests based on IP.
- D
Enable VPC Flow Logs to capture traffic from the IP address.
Why wrong: Flow Logs only capture traffic data, they don't block.
- E
Update the ALB security group to deny inbound traffic from the IP address.
Security groups act as a virtual firewall for the ALB.
Question 1,056 of 1,750
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.
During an incident, a DevOps engineer needs to block traffic from a specific IP address that is attacking an Application Load Balancer. Which TWO actions can the engineer take to mitigate this?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use AWS WAF to create an IP set rule that blocks the IP address.
AWS WAF (option C) can be integrated with an Application Load Balancer to create a web access control list (web ACL) that includes an IP set rule. This rule can explicitly block traffic from a specific source IP address at the application layer (Layer 7), which is the appropriate layer for an ALB. This allows the engineer to mitigate the attack without modifying network-level components.
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 Amazon CloudFront to block the IP address.
Why it's wrong here
CloudFront can block IPs, but it's an additional layer not directly on the ALB.
- ✗
Modify the network ACL for the ALB's subnet to deny the IP address.
Why it's wrong here
NACLs apply at subnet level, but ALBs operate at layer 7; NACL may not block if traffic goes through other paths.
- ✓
Use AWS WAF to create an IP set rule that blocks the IP address.
Why this is correct
AWS WAF integrates with ALB to filter requests based on IP.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Enable VPC Flow Logs to capture traffic from the IP address.
Why it's wrong here
Flow Logs only capture traffic data, they don't block.
- ✓
Update the ALB security group to deny inbound traffic from the IP address.
Why this is correct
Security groups act as a virtual firewall for the ALB.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse network ACLs (stateless, subnet-level) with security groups (stateful, resource-level) and incorrectly assume NACLs can be applied to an ALB's subnet for granular IP blocking, when in fact security groups are the correct network-level control for an ALB.
Detailed technical explanation
How to think about this question
AWS WAF rules are evaluated in the order defined in the web ACL, and an IP set rule can contain up to 10,000 IP addresses or CIDR ranges. When a request matches a block rule, the ALB returns a 403 Forbidden response to the client, and the request is not forwarded to the target group. Security groups (option E) are stateful and operate at the instance level (or ENI level), but an ALB's security group controls inbound traffic to the ALB itself; updating it to deny a specific IP address is effective because the security group acts as a virtual firewall for the ALB, and the deny rule will be evaluated before any allow rules.
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.
Visual reference
Quick reference
OSI Model Reference
| Layer | Name | PDU | Key Protocols / Devices |
|---|---|---|---|
| 7 | Application | Data | HTTP, HTTPS, DNS, SMTP, FTP, SSH |
| 6 | Presentation | Data | TLS / SSL, JPEG, ASCII encoding |
| 5 | Session | Data | NetBIOS, RPC, SIP |
| 4 | Transport | Segment / Datagram | TCP, UDP |
| 3 | Network | Packet | IP, ICMP, OSPF — Routers |
| 2 | Data Link | Frame | Ethernet, Wi-Fi, PPP — Switches, Bridges |
| 1 | Physical | Bits | Cables, NICs, Hubs, Repeaters |
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.
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FAQ
Questions learners often ask
What does this DOP-C02 question test?
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: Use AWS WAF to create an IP set rule that blocks the IP address. — AWS WAF (option C) can be integrated with an Application Load Balancer to create a web access control list (web ACL) that includes an IP set rule. This rule can explicitly block traffic from a specific source IP address at the application layer (Layer 7), which is the appropriate layer for an ALB. This allows the engineer to mitigate the attack without modifying network-level components.
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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Last reviewed: Jul 4, 2026
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