Comprehensive and Detailed Explanation From FortiOS 7.6, FortiWeb 7.4 Exact Extract study guide:

According to the FortiOS 7.6 AWS Administration Guide and the Public Cloud Security documentation regarding AWS VPC Flow Logs, the level at which a flow log is created determines the scope of the data collected:

Flow Log Scope and Hierarchy (Option A): AWS VPC Flow Logs can be created at three different levels: VPC , Subnet , or Network Interface (ENI) .

As seen in the exhibit (VPC flow log wizard), the flow log is being created for the resource vpc-09d6e4631cd49d2b3. When a flow log is created at the VPC level , it captures IP traffic for all network interfaces within that VPC.

To isolate traffic specifically for a single FortiGate EC2 instance and avoid seeing traffic from other instances in the same VPC or subnet, the administrator must create a flow log at the Network Interface level . This provides the most granular visibility and ensures the logs only contain traffic associated with the specific ENIs of that FortiGate instance.

Why other options are incorrect:

Option B: Changing the maximum aggregation interval from 10 minutes to 1 minute increases the frequency of log delivery and captures shorter-lived flows more accurately, but it does not change the scope of the resources being monitored.

Option C: This is a general troubleshooting statement and not a configuration action within the AWS Flow Log wizard that would filter the traffic by instance.

Option D: Changing the destination to Amazon Data Firehose changes how the logs are processed and delivered (e.g., for streaming to a SIEM), but the source data is still determined by the resource level selected (VPC vs. Interface).