A log metric filter and alert should exist for cloud storage bucket IAM changes


It is recommended that a metric filter and alarm be established for Cloud Storage Bucket IAM changes.


Monitoring changes to cloud storage bucket permissions may reduce the time needed to detect and correct permissions on sensitive cloud storage buckets and objects inside the bucket.


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


From the console:

Create the prescribed log metric

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

  2. Click the down arrow icon on the Filter Bar at the top right corner and select Convert to Advanced Filter.

  3. Clear any text and add:

    AND protoPayload.methodName="storage.setIamPermissions"
  4. Click Submit Filter. Display logs appear based on the filter text.

  5. In the Metric Editor menu on the right, fill out the name field. Set Units to 1 (default) and Type to Counter. This ensures that the log metric counts the number of log entries matching your advanced logs query.

  6. Click Create Metric.

Create the 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 it 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 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 Cloud Storage IAM Permission 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:

  1. Create the prescribed log metric using the following command:

    gcloud beta logging metrics create

    See the command usage reference for more information.

  2. Create the prescribed alert policy using the following command:

    gcloud alpha monitoring policies create

    See the command usage reference for more information.


  1. https://console.cloud.google.com/logs/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/overview
  6. https://cloud.google.com/storage/docs/access-control/iam-roles
  7. https://cloud.google.com/sdk/gcloud/reference/beta/logging/metrics/create
  8. https://cloud.google.com/sdk/gcloud/reference/alpha/monitoring/policies/create