This SCS-C02 practice question tests your understanding of security logging and monitoring. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. A key principle to apply: iAM Policy Principal. 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.
The IAM policy above is attached to a role used by an EC2 instance to send logs to CloudWatch Logs. The instance is unable to send logs. What is the MOST likely issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The policy is designed for the CloudWatch Logs service, not for an EC2 instance role.
The IAM policy shown in the question is a resource-based policy designed for CloudWatch Logs (e.g., it may use a `Principal` element or be scoped to CloudWatch Logs actions like `logs:PutLogEvents` with a resource ARN). When attached to an EC2 instance role, an identity-based policy is required, not a resource-based policy. The policy lacks the proper format and permissions for an identity-based role, causing the instance to be unable to send logs. The most likely issue is that the policy is intended for direct CloudWatch Logs service access, not for use with an EC2 instance role.
Key principle: IAM Policy Principal
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
The policy is designed for the CloudWatch Logs service, not for an EC2 instance role.
Why this is correct
The principal is logs.amazonaws.com, but the role should have these actions without principal restriction.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
IAM Policy Principal
✗
The policy does not include logs:DescribeLogGroups.
Why it's wrong here
DescribeLogGroups is not needed for sending logs.
✗
The resource ARN is incorrect.
Why it's wrong here
The ARN is correct for the log group.
✗
The log group does not exist.
Why it's wrong here
The policy does not require log group existence for the actions.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap is that candidates often look for missing permissions (like `logs:DescribeLogGroups`) or incorrect ARNs, but the real issue is that the policy has a Principal element that makes it a service-specific policy for CloudWatch Logs, not an identity-based policy for an EC2 instance role.
Detailed technical explanation
How to think about this question
Under the hood, an EC2 instance role uses AWS Security Token Service (STS) to obtain temporary credentials via `AssumeRole`, and the attached IAM policy must include `sts:AssumeRole` in the trust policy (or the instance profile must be correctly associated). The CloudWatch Logs agent or SDK on the instance uses these credentials to call `PutLogEvents`, which requires the `logs:PutLogEvents` permission on the log stream ARN. A common subtlety is that the resource ARN in the policy must match the log group and stream pattern (e.g., `arn:aws:logs:region:account-id:log-group:my-log-group:log-stream:*`), and if the policy uses a wildcard incorrectly, it may fail silently.
KKey Concepts to Remember
IAM Policy Principal
EC2 Instance Role
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
IAM Policy Principal
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.
Review iAM Policy Principal, then practise related SCS-C02 questions on the same topic to reinforce the concept.
Security Logging and Monitoring — This question tests Security Logging and Monitoring — IAM Policy Principal.
What is the correct answer to this question?
The correct answer is: The policy is designed for the CloudWatch Logs service, not for an EC2 instance role. — The IAM policy shown in the question is a resource-based policy designed for CloudWatch Logs (e.g., it may use a `Principal` element or be scoped to CloudWatch Logs actions like `logs:PutLogEvents` with a resource ARN). When attached to an EC2 instance role, an identity-based policy is required, not a resource-based policy. The policy lacks the proper format and permissions for an identity-based role, causing the instance to be unable to send logs. The most likely issue is that the policy is intended for direct CloudWatch Logs service access, not for use with an EC2 instance role.
What should I do if I get this SCS-C02 question wrong?
Review iAM Policy Principal, then practise related SCS-C02 questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
IAM Policy Principal
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Question Discussion
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