Control: 3.7 Ensure that 'Public access level' is disabled for storage accounts with blob containers

Description

Disallowing public access for a storage account overrides the public access settings for individual containers in that storage account.

The default configuration for a storage account permits a user with appropriate permissions to configure public (anonymous) access to containers and blobs in a storage account. Keep in mind that public access to a container is always turned off by default and must be explicitly configured to permit anonymous requests. It grants read- only access to these resources without sharing the account key, and without requiring a shared access signature. It is recommended not to provide anonymous access to blob containers until, and unless, it is strongly desired. A shared access signature token or Azure AD RBAC should be used for providing controlled and timed access to blob containers. If no anonymous access is needed on any container in the storage account, it’s recommended to set allowBlobPublicAccess false at the account level, which forbids any container to accept anonymous access in the future.

Remediation

From Azure Portal

First, follow Microsoft documentation and create shared access signature tokens for your blob containers. Then,

1. Go to Storage Accounts.
2. For each storage account, go to Networking in Security + networking.
3. Set Public Network Access to Disabled if no anonymous access is needed on the storage account.

From Azure CLI

Set 'Public Network Access' to Disabled on the storage account

1. Set 'Allow Blob Public Access' to false on the storage account

az storage account update --name <storage-account> --resource-group <resource-group> --public-network-access Disabled

From PowerShell

For each Storage Account, run the following to set the PublicNetworkAccess setting to Disabled.

Set-AzStorageAccount -ResourceGroupName <resource group name> -Name <storage account name> -PublicNetworkAccess Disabled

Default Value

By default, Public Network Access is set to Enabled from all networks for the Storage Account.