Ensure that Cloud Storage bucket is not anonymously or publicly accessible - google_storage_bucket_access_control

Description:

It is recommended that IAM policy on Cloud Storage bucket does not allows anonymous or public access.

Rationale:

Allowing anonymous or public access grants permissions to anyone to access bucket content. Such access might not be desired if you are storing any sensitive data. Hence, ensure that anonymous or public access to a bucket is not allowed.

No storage buckets would be publicly accessible. You would have to explicitly administer bucket access.

From Console:

1. Go to 'Storage browser' by visiting https://console.cloud.google.com/storage/browser.
2. Click on the bucket name to go to its 'Bucket details' page.
3. Click on the 'Permissions' tab.
4. Click 'Delete' button in front of 'allUsers' and 'allAuthenticatedUsers' to remove that particular role assignment.

From Command Line:

Remove 'allUsers' and 'allAuthenticatedUsers' access.

gsutil iam ch -d allUsers gs://BUCKET_NAME
gsutil iam ch -d allAuthenticatedUsers gs://BUCKET_NAME

Prevention:

You can prevent Storage buckets from becoming publicly accessible by setting up the 'Domain restricted sharing' organization policy at: https://console.cloud.google.com/iam-admin/orgpolicies/iam-allowedPolicyMemberDomains .