A security engineer configured VPC Flow Logs to publish to Amazon CloudWatch Logs. After 10 minutes, no logs appear. The issue is isolated to the IAM role associated with VPC Flow Logs.
What could be the reason?
A.
logs:GetLogEvents is missing.
B.
The engineer cannot assume the role.
C.
The vpc-flow-logs.amazonaws.com principal cannot assume the role.
VPC Flow Logs require an IAM role that CloudWatch Logs can use to publish flow log records. AWS documentation and AWS Certified Security – Specialty materials explain that the VPC Flow Logs service must be able to assume the IAM role through its trust policy. The trust relationship must include the service principal vpc-flow-logs.amazonaws.com. If the trust policy does not allow this principal to assume the role, flow logs cannot be delivered and no records will appear in the CloudWatch Logs log group even when traffic exists. logs:GetLogEvents is not required for delivery; it is used for reading logs. The security engineer’s ability to assume the role is not relevant because the service, not the engineer, assumes it. Tagging permissions are not required for basic log delivery. Therefore, the most likely cause is an incorrect trust policy that prevents the VPC Flow Logs service principal from assuming the role.
Referenced AWS Specialty Documents:
AWS Certified Security – Specialty Official Study Guide
Amazon VPC Flow Logs IAM Role Requirements
IAM Trust Policies for AWS Services
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