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Description

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

Rationale​

Monitoring for Create or Update Firewall rule events gives insight to network access changes and may reduce the time it takes to detect suspicious activity.

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 at least one metric <Log_Metric_Name> is present with this filter text:

     resource.type="gce_firewall_rule" 
     AND (protoPayload.methodName:"compute.firewalls.patch" 
     OR protoPayload.methodName:"compute.firewalls.insert" 
     OR protoPayload.methodName:"compute.firewalls.delete")

Ensure that 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 zero(0) for greater than zero(0) seconds means that the alert will trigger for any new owner change. Verify that the chosen alerting thresholds make sense for the user's organization.
  3. Ensure that appropriate notification channels have been set up.

From Google Cloud CLI​

Ensure that 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_firewall_rule" 
      AND (protoPayload.methodName:"compute.firewalls.patch" 
      OR protoPayload.methodName:"compute.firewalls.insert" 
      OR protoPayload.methodName:"compute.firewalls.delete")

  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/vpc/docs/firewalls