Cis Azure Foundations 9.3.2.2

Ensure 'Public Network Access' is 'Disabled' for storage accounts

Description

Disable public network access to prevent exposure to the internet and reduce the risk of unauthorized access. Use private endpoints to securely manage access within trusted networks.

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

Rationale

Disabling public network access improves security by ensuring that a storage account is not exposed on the public internet. The default network configuration for a storage account permits a user with appropriate permissions to configure public network access to containers and blobs in a storage account. It is recommended not to provide public network access to storage accounts 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.

Impact

NOTE: Prior to disabling public network access, it is strongly recommended that, for each storage account, either virtual network integration is completed OR private endpoints/links are set up as described in "Ensure Private Endpoints are used to access Storage Accounts."

Disabling public network access restricts direct access to the service. This enhances security but will require the configuration of a virtual network and/or private endpoints for any services or users needing access within trusted networks. Access will have to be managed using shared access signatures or via Azure AD RBAC.

Audit Procedure

Audit from Azure Portal

1. Go to Storage Accounts.
2. For each storage account, under the Security + networking section, click Networking.
3. Ensure the Public network access setting is set to Disabled.

Audit from Azure CLI

Ensure publicNetworkAccess is Disabled:

az storage account show --name <storage-account> --resource-group <resource-group> --query "{publicNetworkAccess:publicNetworkAccess}"

Audit from PowerShell

For each Storage Account, ensure PublicNetworkAccess is Disabled:

Get-AzStorageAccount -Name <storage account name> -ResourceGroupName <resource group name> |select PublicNetworkAccess

Expected Result

PublicNetworkAccess should be Disabled for all storage accounts.

Remediation

Remediate 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, under the Security + networking section, click Networking.
3. Set Public network access to Disabled.
4. Click Save.

Remediate from Azure CLI

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

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

Remediate 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.

References

1. https://learn.microsoft.com/en-us/azure/storage/blobs/anonymous-read-access-configure
2. https://learn.microsoft.com/en-us/security/benchmark/azure/mcsb-governance-strategy#gs-2-define-and-implement-enterprise-segmentationseparation-of-duties-strategy
3. https://learn.microsoft.com/en-us/security/benchmark/azure/mcsb-network-security#ns-2-secure-cloud-native-services-with-network-controls
4. https://learn.microsoft.com/en-us/azure/storage/blobs/assign-azure-role-data-access
5. https://learn.microsoft.com/en-us/azure/storage/common/storage-network-security

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