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3.11 Ensure Soft Delete is Enabled for Azure Containers and Blob Storage (Manual)​

note

This rule has been changed to manual, see Permanently Manual Rules for CIS Azure 1.5.0 for details.

Profile Applicability​

• Level 1

Description​

The Azure Storage blobs contain data like ePHI or Financial, which can be secret or personal. Data that is erroneously modified or deleted by an application or other storage account user will cause data loss or unavailability.

It is recommended that both Azure Containers with attached Blob Storage and standalone containers with Blob Storage be made recoverable by enabling the soft delete configuration. This is to save and recover data when blobs or blob snapshots are deleted.

Rationale​

Containers and Blob Storage data can be incorrectly deleted. An attacker/malicious user may do this deliberately in order to cause disruption. Deleting an Azure Storage blob causes immediate data loss. Enabling this configuration for Azure storage ensures that even if blobs/data were deleted from the storage account, Blobs/data objects are recoverable for a particular time which is set in the "Retention policies," ranging from 7 days to 365 days.

Impact​

Additional storage costs may be incurred as snapshots are retained.

Audit​

From Azure Portal​

  1. From the Azure home page, open the hamburger menu in the top left or click on the arrow pointing right with 'More services' underneath.
  2. Select Storage.
  3. Select Storage Accounts.
  4. For each Storage Account, navigate to Data protection in the left scroll column.
  5. Ensure that soft delete is checked for both blobs and containers. Also check if the retention period is a sufficient length for your organization.

Blob Storage

Ensure that the output of the below command contains enabled status as true and days is not empty or null

az storage blob service-properties delete-policy show --account-name <StorageAccountName> --account-key <accountkey>

Azure Containers Make certain that the --enable-container-delete-retention is 'true'.

az storage account blob-service-properties show
 --account-name <StorageAccountName>
 --account-key <accountkey>
 --resource-group <resource_group>

Remediation​

From Azure Portal​

  1. From the Azure home page, open the hamburger menu in the top left or click on the arrow pointing right with 'More services' underneath.
  2. Select Storage.
  3. Select Storage Accounts.
  4. For each Storage Account, navigate to Data protection in the left scroll column.
  5. Check soft delete for both blobs and containers. Set the retention period to a sufficient length for your organization.

From Azure CLI​

Update blob storage retention days in below command

az storage blob service-properties delete-policy update --days-retained <RetentionDaysValue> --account-name <StorageAccountName> > --account-key <AccountKey> --enable true

Update container retention with the below command

az storage account blob-service-properties update
 --enable-container-delete-retention true
 --container-delete-retention-days <days>
 --account-name <storage-account>
 --resource-group <resource_group>
 --account-key <AccountKey>

References​

https://docs.microsoft.com/en-us/azure/storage/blobs/storage-blob-soft-delete
https://docs.microsoft.com/en-us/azure/storage/blobs/soft-delete-container-overview
https://docs.microsoft.com/en-us/azure/storage/blobs/soft-delete-container-enable?tabs=azure-portal