The answer is to detach the instance from the Auto Scaling group and remove it from the load balancer. This is the correct first step because it immediately stops all incoming traffic to the compromised EC2 instance while preserving the forensic evidence needed for investigation. By removing the instance from the Auto Scaling group, you prevent the group from automatically replacing or terminating it, and by deregistering it from the load balancer, you cut off user traffic without destroying the instance. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of incident response within an Auto Scaling group, where the common trap is to terminate the instance first—but that destroys volatile data and logs. A memory tip: remember "Detach before Destroy" to prioritize isolation over termination when you need to isolate compromised EC2 in Auto Scaling group.
DOP-C02 Security and Compliance Practice Question
This DOP-C02 practice question tests your understanding of security and compliance. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 DevOps engineer receives an alert that an EC2 instance has been compromised. The instance is part of an Auto Scaling group. What is the first step the engineer should take to isolate the instance?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Detach the instance from the Auto Scaling group and remove it from the load balancer
Detaching the instance from the Auto Scaling group and removing it from the load balancer stops traffic, then security groups can be applied to block all traffic. Option A is wrong because termination may destroy evidence. Option B is wrong because snapshotting does not isolate. Option C is wrong because AMI creation is not immediate isolation.
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.
✗
Create a snapshot of the instance's root volume
Why it's wrong here
Snapshot does not isolate the instance.
✓
Detach the instance from the Auto Scaling group and remove it from the load balancer
Why this is correct
Isolates the instance by stopping traffic and decoupling from ASG.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
Create an AMI of the instance for analysis
Why it's wrong here
AMI creation takes time and does not isolate immediately.
✗
Terminate the instance immediately
Why it's wrong here
Termination destroys forensic evidence.
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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
Got this wrong? Here's your next step.
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 DOP-C02 NAT questions on configuration and troubleshooting.
Security and Compliance — This question tests Security and Compliance — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Detach the instance from the Auto Scaling group and remove it from the load balancer — Detaching the instance from the Auto Scaling group and removing it from the load balancer stops traffic, then security groups can be applied to block all traffic. Option A is wrong because termination may destroy evidence. Option B is wrong because snapshotting does not isolate. Option C is wrong because AMI creation is not immediate isolation.
What should I do if I get this DOP-C02 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 DOP-C02 NAT questions on configuration and troubleshooting.
Are there clue words in this question I should notice?
Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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