Control: 3.8 Ensure Default Network Access Rule for Storage Accounts is Set to Deny

Description

Restricting default network access helps to provide a new layer of security, since storage accounts accept connections from clients on any network. To limit access to selected networks, the default action must be changed.

Storage accounts should be configured to deny access to traffic from all networks (including internet traffic). Access can be granted to traffic from specific Azure Virtual networks, allowing a secure network boundary for specific applications to be built. Access can also be granted to public internet IP address ranges to enable connections from specific internet or on-premises clients. When network rules are configured, only applications from allowed networks can access a storage account. When calling from an allowed network, applications continue to require proper authorization (a valid access key or SAS token) to access the storage account.

Remediation

From Azure Console

Go to Storage Accounts.
For each storage account, Click on the Networking blade.
Click the Firewalls and virtual networks heading.
Ensure that you have elected to allow access from Selected networks.
Add rules to allow traffic from specific network.
Click Save to apply your changes.

From Azure CLI

Use the below command to update default-action to Deny.

az storage account update --name <StorageAccountName> --resource-group <resourceGroupName> --default-action Deny

Default Value

By default, Storage Accounts will accept connections from clients on any network.

Usage

Run the control in your terminal:

powerpipe control run azure_compliance.control.cis_v200_3_8

Snapshot and share results via Turbot Pipes:

powerpipe login
powerpipe control run azure_compliance.control.cis_v200_3_8 --share

SQL

This control uses a named query:

select
  sa.id as resource,
  case
    when sa.network_rule_default_action = 'Allow' then 'alarm'
    else 'ok'
  end as status,
  case
    when sa.network_rule_default_action = 'Allow' then name || ' allows traffic from all networks.'
    else name || ' allows traffic from specific networks.'
  end as reason
  
  , sa.resource_group as resource_group
  , sub.display_name as subscription
from
  azure_storage_account sa,
  azure_subscription sub
where
  sub.subscription_id = sa.subscription_id;