Ensure That the Log Metric Filter and Alerts Exist for Cloud Storage IAM Permission Changes

Description:

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

Rationale:

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. These charges could be significant depending on the size of the organization.

From Google Cloud 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. Click the down arrow symbol on the 'Filter Bar' at the rightmost corner and select 'Convert to Advanced Filter'.

3. Clear any text and add:

resource.type="gcs_bucket"
AND protoPayload.methodName="storage.setIamPermissions"

4. Click 'Submit Filter'. Display logs appear based on the filter text entered by the user.

5. In the 'Metric Editor' menu on 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 the user's advanced logs query.

6. Click 'Create Metric'.

Create the prescribed Alert Policy:

1. Identify the newly created metric under the section 'User-defined Metrics' at https://console.cloud.google.com/logs/metrics.

2. Click the 3-dot icon in the rightmost column for the new metric and select 'Create alert from Metric'. A new page appears.

3. Fill out the alert policy configuration and click 'Save'. Choose the alerting threshold and configuration that makes sense for the user's organization. For example, a threshold of zero(0) for the most recent value will ensure that a notification is triggered for every owner change in the project:

Set 'Aggregator' to 'Count'

Set 'Configuration':

• Condition: above

• Threshold: 0

• For: most recent value

4. Configure the desired notifications channels in the section 'Notifications'.

5. Name the policy and click 'Save'.

From Google Cloud CLI

Create the prescribed Log Metric:

• Use the command: gcloud beta logging metrics create

Create the prescribed alert policy:

• Use the command: gcloud alpha monitoring policies create