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3.8 Ensure Default Network Access Rule for Storage Accounts is Set to Deny (Automated)​

Profile Applicability​

• Level 1

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.

Rationale​

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.

Impact​

All allowed networks will need to be whitelisted on each specific network, creating administrative overhead. This may result in loss of network connectivity, so do not turn on for critical resources during business hours.

Audit​

From Azure Console​

  1. Go to Storage Accounts
  2. For each storage account, Click on the Networking blade.
  3. Click the Firewalls and virtual networks heading.
  4. Ensure that Allow access from All networks is not selected.

From Azure CLI​

Ensure defaultAction is not set to Allow.

 az storage account list --query '[*].networkRuleSet'

From Azure PowerShell​

Connect-AzAccount
Set-AzContext -Subscription <subscription ID>
Get-AzStorageAccountNetworkRuleset -ResourceGroupName <resource group> -Name <storage account name> |Select-Object DefaultAction

PowerShell Result - Non-Compliant

DefaultAction : Allow

PowerShell Result - Compliant

DefaultAction : Deny

Remediation​

From Azure Console​

  1. Go to Storage Accounts
  2. For each storage account, Click on the Networking blade
  3. Click the Firewalls and virtual networks heading.
  4. Ensure that you have elected to allow access from Selected networks
  5. Add rules to allow traffic from specific network.
  6. 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

References​

https://docs.microsoft.com/en-us/azure/storage/common/storage-network-security
https://docs.microsoft.com/en-us/security/benchmark/azure/security-controls-v3-governance-strategy#gs-2-define-and-implement-enterprise-segmentationseparation-of-duties-strategy
https://docs.microsoft.com/en-us/security/benchmark/azure/security-controls-v3-network-security#ns-2-secure-cloud-services-with-network-controls