- A
Use EventBridge to trigger a Lambda function in the delegated administrator account, which assumes an IAM role in the affected account to isolate the instance.
This is the recommended pattern for cross-account automated response.
- B
Configure GuardDuty to invoke a Lambda function in the affected account directly.
Why wrong: GuardDuty cannot invoke Lambda directly; it uses EventBridge. Also, cross-account invocation requires proper permissions.
- C
Use EventBridge to send the finding to a Step Functions workflow that isolates the instance.
Why wrong: Step Functions is possible but adds complexity; Lambda alone can handle isolation.
- D
Use AWS Systems Manager Automation to isolate the instance across accounts.
Why wrong: Systems Manager Automation can isolate, but cross-account setup is more complex than Lambda with role assumption.
Quick Answer
The answer is to use EventBridge to trigger a Lambda function in the delegated administrator account, which assumes an IAM role in the affected member account to isolate the EC2 instance. This architecture is correct because it centralizes the automated EC2 isolation response to GuardDuty findings while respecting the security boundary between accounts—the Lambda function in the delegated admin account uses STS AssumeRole to gain temporary, scoped permissions in the affected account, avoiding the need for cross-account credentials or a single monolithic account. On the AWS Certified Security Specialty SCS-C02 exam, this pattern tests your understanding of cross-account automation with EventBridge, Lambda, and IAM roles, and a common trap is choosing a solution that places the Lambda function directly in the member account, which breaks centralized management. Remember the mnemonic “DEL-ASSUME”: Delegated admin EventBridge triggers Lambda, which Assumes a role in the member account to isolate.
SCS-C02 Threat Detection and Incident Response Practice Question
This SCS-C02 practice question tests your understanding of threat detection and incident 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.
An organization uses AWS Organizations with hundreds of accounts. The security team wants to automatically respond to a specific GuardDuty finding by isolating the affected EC2 instance. What is the recommended architecture?
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 EventBridge to trigger a Lambda function in the delegated administrator account, which assumes an IAM role in the affected account to isolate the instance.
Option A is correct because it follows the recommended architecture for cross-account automated response to GuardDuty findings. EventBridge in the delegated administrator account captures the finding and triggers a Lambda function, which then assumes an IAM role (using STS AssumeRole) in the affected member account to perform the isolation. This pattern centralizes management while respecting the security boundary between accounts.
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.
- ✓
Use EventBridge to trigger a Lambda function in the delegated administrator account, which assumes an IAM role in the affected account to isolate the instance.
Why this is correct
This is the recommended pattern for cross-account automated response.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Configure GuardDuty to invoke a Lambda function in the affected account directly.
Why it's wrong here
GuardDuty cannot invoke Lambda directly; it uses EventBridge. Also, cross-account invocation requires proper permissions.
- ✗
Use EventBridge to send the finding to a Step Functions workflow that isolates the instance.
Why it's wrong here
Step Functions is possible but adds complexity; Lambda alone can handle isolation.
- ✗
Use AWS Systems Manager Automation to isolate the instance across accounts.
Why it's wrong here
Systems Manager Automation can isolate, but cross-account setup is more complex than Lambda with role assumption.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may assume GuardDuty can directly trigger a Lambda in any account, but in reality, GuardDuty findings are centralized in the delegated administrator account and cross-account actions require explicit role assumption via EventBridge and Lambda.
Detailed technical explanation
How to think about this question
Under the hood, the Lambda function uses the AWS SDK to call sts:AssumeRole with the target account's IAM role ARN (which must have a trust policy allowing the administrator account). The isolated instance is typically achieved by modifying the EC2 instance's security group to deny all traffic or by attaching a new security group with no inbound/outbound rules. This pattern is documented in the AWS Security Incident Response Guide and is preferred because it keeps the response logic centralized in the delegated administrator account, avoiding the need to deploy Lambda functions in every member account.
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.
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FAQ
Questions learners often ask
What does this SCS-C02 question test?
Threat Detection and Incident Response — This question tests Threat Detection and Incident Response — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use EventBridge to trigger a Lambda function in the delegated administrator account, which assumes an IAM role in the affected account to isolate the instance. — Option A is correct because it follows the recommended architecture for cross-account automated response to GuardDuty findings. EventBridge in the delegated administrator account captures the finding and triggers a Lambda function, which then assumes an IAM role (using STS AssumeRole) in the affected member account to perform the isolation. This pattern centralizes management while respecting the security boundary between accounts.
What should I do if I get this SCS-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: Jun 24, 2026
This SCS-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SCS-C02 exam.
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