Details
Flow Logs is a feature that enables users to capture information about the IP traffic going to and from network interfaces in the organization’s VPC Subnets. Once a flow log is created, the user can view and retrieve its data in Stackdriver Logging. It is recommended that Flow Logs be enabled for every business-critical VPC subnet.
Rationale:
VPC networks and subnetworks not reserved for internal HTTP(S) load balancing provide logically isolated and secure network partitions where GCP resources can be launched. When Flow Logs are enabled for a subnet, VMs within that subnet start reporting on all Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) flows. Each VM samples the TCP and UDP flows it sees, inbound and outbound, whether the flow is to or from another VM, a host in the on-premises datacenter, a Google service, or a host on the Internet. If two GCP VMs are communicating, and both are in subnets that have VPC Flow Logs enabled, both VMs report the flows.
Flow Logs supports the following use cases:
Network monitoring
Understanding network usage and optimizing network traffic expenses
Network forensics
Real-time security analysis
Flow Logs provide visibility into network traffic for each VM inside the subnet and can be used to detect anomalous traffic or provide insight during security workflows.
Note: Subnets reserved for use by internal HTTP(S) load balancers do not support VPC flow logs.
Impact:
Standard pricing for Stackdriver Logging, BigQuery, or Cloud Pub/Sub applies. VPC Flow Logs generation will be charged starting in GA as described in reference: https://cloud.google.com/vpc/
Solution
From Console:
Go to the VPC network GCP Console visiting https://console.cloud.google.com/networking/networks/list
Click the name of a subnet, The Subnet details page displays.
Click the EDIT button.
Set Flow Logs to On.
Click Save.
From Command Line:
To set Private Google access for a network subnet, run the following command:
gcloud compute networks subnets update [SUBNET_NAME] –region [REGION] –enable-flow-logs
Default Value:
By default, Flow Logs is set to Off when a new VPC network subnet is created.
Supportive Information
The following resource is also helpful.
This security hardening control applies to the following category of controls within NIST 800-53: Audit and Accountability, System and Information Integrity.This control applies to the following type of system GCP.