Ensure 'Allow Blob Anonymous Access' is set to 'Disabled'

Overview

The Azure Storage setting Allow Blob Anonymous Access (a.k.a. allowBlobPublicAccess) controls whether anonymous access is allowed for blob data in a storage account. When this property is set to True, it enables public read access to blob data, which can be convenient for sharing data but may carry security risks. When set to False, it disallows public access to blob data, providing a more secure storage environment.

Rationale

If "Allow Blob Anonymous Access" is enabled, blobs can be accessed by adding the blob name to the URL to see the contents. An attacker can enumerate a blob using methods such as brute force and access them.

If this setting is set to 'Enabled', data may be exfiltrated by brute-force enumeration of items from a storage account.

Impact

Additional consideration may be required in exceptional circumstances where elements of a storage account require public accessibility. In these circumstances, it is highly recommended that all data stored in the public-facing storage account be reviewed for sensitive or potentially compromising data and that sensitive or compromising data never be stored in these storage accounts.

Default Value

Disabled

Remediation guidance

From Azure Console

Open the storage account in the Azure Portal using the Open in Azure button.
Click on a Storage Account.
Under the Settings section, click Configuration.
Under Allow Blob Anonymous Access, select Disabled.

Repeat these steps for each Storage Account.

From Azure Powershell

For every storage account in scope, run the following:

$storageAccount = Get-AzStorageAccount -ResourceGroupName "<yourResourceGroup>" -Name "<yourStorageAccountName>"
$storageAccount.AllowBlobPublicAccess = $false
Set-AzStorageAccount -InputObject $storageAccount

Multiple Remediation Paths

Azure

SERVICE-WIDE (RECOMMENDED when many resources are affected): Assign Azure Policy initiatives at management group/subscription scope and trigger remediation tasks.

az policy assignment create --name <assignment-name> --scope /subscriptions/<subscription-id> --policy-set-definition <initiative-id>
az policy remediation create --name <remediation-name> --policy-assignment <assignment-id>

ASSET-LEVEL: Apply the resource-specific remediation steps above to the listed non-compliant resources.

PREVENTIVE: Embed Azure Policy checks into landing zones and IaC workflows to block or auto-remediate drift.

References for Service-Wide Patterns

Azure Policy overview: https://learn.microsoft.com/en-us/azure/governance/policy/overview
Azure Policy remediation: https://learn.microsoft.com/en-us/azure/governance/policy/how-to/remediate-resources
Azure Policy initiative structure: https://learn.microsoft.com/en-us/azure/governance/policy/concepts/initiative-definition-structure

Operational Rollout Workflow

Use this sequence to reduce risk and avoid repeated drift.

1. Contain at Service-Wide Scope First (Recommended)

Azure: assign policy initiatives at management group/subscription scope and run remediation tasks.

az policy assignment create --name <assignment-name> --scope /subscriptions/<subscription-id> --policy-set-definition <initiative-id>
az policy remediation create --name <remediation-name> --policy-assignment <assignment-id>

2. Remediate Existing Affected Assets

Execute the control-specific Console/CLI steps documented above for each flagged resource.
Prioritize internet-exposed and production assets first.

3. Validate and Prevent Recurrence

Re-scan after each remediation batch.
Track exceptions with owner and expiry date.
Add preventive checks in IaC/CI pipelines.

Query logic

These are the stored checks tied to this control.

Azure Storage Accounts Allowing Blob Public Access

Connectors

Microsoft Azure

Covered asset types

StorageAccount

Expected check: eq []

{
  storageAccounts(where: { allowBlobPublicAccess: true }) {
    ...AssetFragment
  }
}