Description

Virtual Machine Disks and snapshots can be configured to allow access from different network resources.

Rationale

The setting Enable public access from all networks is, in many cases, an overly permissive setting on Virtual Machine Disks that presents atypical attack, data infiltration, and data exfiltration vectors. If a disk to network connection is required, the preferred setting is to Disable public access and enable private access.

Impact

The setting Disable public access and enable private access will require configuring a private link (URL in references below).

The setting Disable public and private access is most secure and preferred where disk network access is not needed.

Audit

From Azure Portal

Part A. Select the Virtual Machine to Evaluate

Using the search bar, search for and open the Virtual Machines service.
Click on the name of the Virtual Machine to be audited.

Part B. Evaluate each Virtual Machine Disk individually

From the selected Virtual Machine resource window, expand the Settings menu item and click Disks.
For each disk, click the name of the disk to open the disk resource window.
From the selected Disk resource window, expand the Settings menu item, and click Networking.

Ensure that Network access is NOT set to Enable public access from all networks.

Repeat Part B for each Disk attached to a VM.

Repeat Parts A and B to evaluate all Disks in all VMs.

From Azure CLI

For each managed disk, run the following command:

az disk show --disk-name <disk name> --resource-group <resource group name>

Ensure the publicNetworkAccess setting is set to Disabled and the networkAccessPolicy setting is set to AllowPrivate or DenyAll.

From PowerShell

For each managed disk, run the following PowerShell command:

Get-AzDisk -ResourceGroupName <resource group name> -DiskName <disk name>

Ensure the PublicNetworkAccess setting is Disabled and the NetworkAccessPolicy is set to AllowPrivate or DenyAll.

From Azure Policy

If referencing a digital copy of this Benchmark, clicking a Policy ID will open a link to the associated Policy definition in Azure.

Policy ID: 8405fdab-1faf-48aa-b702-999c9c172094 - Name: Managed disks should disable public network access

Default Value

By default, Disk Network access is set to Enable public access from all networks.

Rationale​

Impact​

Audit​

From Azure Portal​

Part A. Select the Virtual Machine to Evaluate​

Part B. Evaluate each Virtual Machine Disk individually​

From Azure CLI​

From PowerShell​

From Azure Policy​

Default Value​

References​