A log metric filter and alert should exist for VPC firewall rule changes

Description

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

Rationale

Monitoring 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 logging may result in your project being charged for the additional logs usage.

Remediation

From the console

Create the prescribed log metric

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

  2. Set Metric Type to Counter. This ensures that the log metric counts the number of log entries matching the user’s advanced logs query.

  3. Fill out the Log metric name field.

  4. Set the Units to 1 (default).

  5. Under Filter selection, add the following text to the Build filter block:

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

  6. Click Create Metric

Create a prescribed alert policy

  1. Go to https://console.cloud.google.com/logs/metrics. Under the User-defined Metrics section, identify the newly created metric.
  2. Click the kebab icon in the rightmost column for the new metric and select Create alert from Metric.
  3. Leave the Enter a Monitoring filter field as is.
  4. Set Rolling window function to delta.
  5. Under Across time series, set the Time series aggregation field to count.
  6. Navigate to Configure trigger using the left-hand panel and leave the default value of threshold for Condition type.
  7. Choose the alerting threshold and trigger conditions that make most sense for your organization. For example, a Threshold value of 0 and an Alert trigger of Any time series violates ensures that a notification is triggered for every VPC network firewall rule change in the project.
  8. Navigate to Notifications and name to configure your desired notification channel and alerting policy name.
  9. Navigate to Review alert and validate that all values look as expected. Then, click CREATE POLICY.

From the command line

Create a prescribed log metric

Use the command: gcloud beta logging metrics create Reference for command usage: https://cloud.google.com/sdk/gcloud/reference/beta/logging/metrics/create

Create a prescribed alert policy

Use the command: gcloud alpha monitoring policies create Reference for command usage: https://cloud.google.com/sdk/gcloud/reference/alpha/monitoring/policies/create

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