The answer is that the IAM policy’s resource ARN is missing the log group itself, which causes write failures because Lambda’s initial API call to CloudWatch Logs targets the log group resource, not just the log streams. The policy grants `logs:CreateLogStream` and `logs:PutLogEvents` on `arn:aws:logs:us-east-1:123456789012:log-group:MyLogGroup:log-stream:*`, but Lambda first needs `logs:CreateLogGroup` or `logs:DescribeLogGroups` permission on the log group ARN (`arn:aws:logs:us-east-1:123456789012:log-group:MyLogGroup`) to verify or create the group. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding of how resource-level ARN specificity interacts with the order of API calls—a common trap is assuming that stream-level permissions alone are sufficient. Remember the memory tip: “Streams flow from the group, so the group must be in the policy first.”
SCS-C02 Threat Detection and Incident Response Practice Question
This SCS-C02 practice question tests your understanding of threat detection and incident response. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The resource ARN does not include the log group itself; only log streams
The IAM policy grants `logs:CreateLogStream` and `logs:PutLogEvents` but specifies a resource ARN that only covers log streams (`arn:aws:logs:us-east-1:123456789012:log-group:MyLogGroup:log-stream:*`). The Lambda function first needs to write to the log group itself (e.g., to create the log group or confirm its existence), which requires `logs:CreateLogGroup` or `logs:DescribeLogGroups` permissions on the log group resource ARN (`arn:aws:logs:us-east-1:123456789012:log-group:MyLogGroup`). Without that, the initial API call to the log group fails, preventing any log stream creation or log event delivery.
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.
✓
The resource ARN does not include the log group itself; only log streams
Why this is correct
PutLogEvents requires access to the log group resource as well.
Related concept
Read the scenario before looking for a memorised answer.
✗
The actions list does not include logs:DescribeLogGroups
Why it's wrong here
DescribeLogGroups is not required for writing logs.
✗
The policy is missing an explicit deny for other actions
Why it's wrong here
Explicit deny is not needed; default deny applies.
✗
The region in the ARN does not match the Lambda function's region
Why it's wrong here
The region matches us-east-1.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates focus on the actions (e.g., missing `logs:DescribeLogGroups`) rather than the resource ARN, which must include the log group itself (not just log streams) for the initial log group creation or access check.
Detailed technical explanation
How to think about this question
Under the hood, the AWS Lambda runtime uses the AWS SDK to call `CreateLogGroup` on the CloudWatch Logs service before any log stream operations. If the IAM policy only grants permissions on `log-stream` resources, the `CreateLogGroup` call (which targets the log group ARN) is denied by the implicit deny, resulting in an `AccessDeniedException`. This is a common misconfiguration because the CloudWatch Logs API requires separate resource-level permissions for the log group and log stream, and the log group ARN must be explicitly allowed for the initial creation or verification step.
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.
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: The resource ARN does not include the log group itself; only log streams — The IAM policy grants `logs:CreateLogStream` and `logs:PutLogEvents` but specifies a resource ARN that only covers log streams (`arn:aws:logs:us-east-1:123456789012:log-group:MyLogGroup:log-stream:*`). The Lambda function first needs to write to the log group itself (e.g., to create the log group or confirm its existence), which requires `logs:CreateLogGroup` or `logs:DescribeLogGroups` permissions on the log group resource ARN (`arn:aws:logs:us-east-1:123456789012:log-group:MyLogGroup`). Without that, the initial API call to the log group fails, preventing any log stream creation or log event delivery.
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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Question Discussion
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