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Description

It is recommended that a metric filter and alarm be established for Virtual Private Cloud (VPC) network route changes.

Rationale​

Google Cloud Platform (GCP) routes define the paths network traffic takes from a VM instance to another destination. The other destination can be inside the organization VPC network (such as another VM) or outside of it. Every route consists of a destination and a next hop. Traffic whose destination IP is within the destination range is sent to the next hop for delivery.

Monitoring changes to route tables will help ensure that all VPC traffic flows through an expected path.

Impact​

Enabling of logging may result in your project being charged for the additional logs usage. These charges could be significant depending on the size of the organization.

Audit​

From Google Cloud Console​

Ensure that the prescribed Log metric is present:

  1. Go to Logging/Logs-based Metrics by visiting https://console.cloud.google.com/logs/metrics.

  2. In the User-defined Metrics section, ensure that at least one metric <Log_Metric_Name> is present with the filter text:

     resource.type="gce_route" 
     AND (protoPayload.methodName:"compute.routes.delete" 
     OR protoPayload.methodName:"compute.routes.insert")

Ensure the prescribed alerting policy is present:

  1. Go to Alerting by visiting: https://console.cloud.google.com/monitoring/alerting.
  2. Under the Policies section, ensure that at least one alert policy exists for the log metric above. Clicking on the policy should show that it is configured with a condition. For example, Violates when: Any logging.googleapis.com/user/<Log Metric Name> stream is above a threshold of 0 for greater than zero(0) seconds means that the alert will trigger for any new owner change. Verify that the chosen alert thresholds make sense for the user's organization.
  3. Ensure that the appropriate notification channels have been set up.

From Google Cloud CLI​

Ensure the prescribed log metric is present:

  1. List the log metrics:

     gcloud logging metrics list --format json

  2. Ensure that the output contains at least one metric with the filter set to:

      resource.type="gce_route" 
      ND (protoPayload.methodName:"compute.routes.delete" 
      OR protoPayload.methodName:"compute.routes.insert")

  3. Note the value of the property metricDescriptor.type for the identified metric, in the format logging.googleapis.com/user/<Log Metric Name>.

Ensure that the prescribed alerting policy is present:

  1. List the alerting policies:

     gcloud alpha monitoring policies list --format json

  2. Ensure that the output contains an least one alert policy where:

    • conditions.conditionThreshold.filter is set to metric.type=\"logging.googleapis.com/user/<Log Metric Name>\"

    • AND enabled is set to true

References​

  1. https://cloud.google.com/logging/docs/logs-based-metrics/
  2. https://cloud.google.com/monitoring/custom-metrics/
  3. https://cloud.google.com/monitoring/alerts/
  4. https://cloud.google.com/logging/docs/reference/tools/gcloud-logging
  5. https://cloud.google.com/storage/docs/access-control/iam
  6. https://cloud.google.com/sdk/gcloud/reference/beta/logging/metrics/create
  7. https://cloud.google.com/sdk/gcloud/reference/alpha/monitoring/policies/create