Cis Azure Foundations 9.1.1

Ensure soft delete for Azure File Shares is Enabled

Description

Azure Files offers soft delete for file shares, allowing you to easily recover your data when it is mistakenly deleted by an application or another storage account user.

Rationale

Important data could be accidentally deleted or removed by a malicious actor. With soft delete enabled, the data is retained for the defined retention period before permanent deletion, allowing for recovery of the data.

Impact

When a file share is soft-deleted, the used portion of the storage is charged for the indicated soft-deleted period. All other meters are not charged unless the share is restored.

Audit Procedure

Audit from Azure Portal

1. Go to Storage Accounts.
2. For each storage account with file shares, under Data storage, click on File shares.
3. Under File share settings, ensure the value for Soft delete shows a number of days between 1 and 365, inclusive.

Audit from Azure CLI

Run the following command to list storage accounts:

az storage account list

Run the following command to determine if a storage account has file shares:

az storage share list --account-name <storage-account>

For each storage account with file shares, run the following command:

az storage account file-service-properties show --resource-group <resource-group> --account-name <storage-account>

Ensure that under shareDeleteRetentionPolicy, enabled is set to true, and days is set to an appropriate value between 1 and 365, inclusive.

Audit from PowerShell

Run the following command to list storage accounts:

Get-AzStorageAccount -ResourceGroupName <resource-group>

With a storage account context set, run the following command to determine if a storage account has file shares:

Get-AzStorageShare

For each storage account with file shares, run the following command:

Get-AzStorageFileServiceProperty -ResourceGroupName <resource-group> -AccountName <storage-account>

Ensure that ShareDeleteRetentionPolicy.Enabled is set to True and ShareDeleteRetentionPolicy.Days is set to an appropriate value between 1 and 365, inclusive.

Expected Result

shareDeleteRetentionPolicy.enabled should be true with days between 1 and 365.

Remediation

Remediate from Azure Portal

1. Go to Storage Accounts.
2. For each storage account with file shares, under Data storage, click File shares.
3. Under File share settings, click the value next to Soft delete.
4. Under Soft delete for all file shares, click the toggle to set it to Enabled.
5. Under Retention policies, set an appropriate number of days to retain soft deleted data between 1 and 365, inclusive.
6. Click Save.

Remediate from Azure CLI

For each storage account requiring remediation, run the following command to enable soft delete for file shares and set an appropriate number of days for deleted data to be retained, between 1 and 365, inclusive:

az storage account file-service-properties update --account-name <storage-account> --enable-delete-retention true --delete-retention-days <retention-days>

Remediate from PowerShell

For each storage account requiring remediation, run the following command to enable soft delete for file shares and set an appropriate number of days for deleted data to be retained, between 1 and 365, inclusive:

Update-AzStorageFileServiceProperty -ResourceGroupName <resource-group> -AccountName <storage-account> -EnableShareDeleteRetentionPolicy $true -ShareRetentionDays <retention-days>

Default Value

Soft delete is enabled by default at the storage account file share setting level.

References

1. https://learn.microsoft.com/en-us/azure/storage/files/storage-files-enable-soft-delete
2. https://learn.microsoft.com/en-us/cli/azure/storage/account/file-service-properties
3. https://learn.microsoft.com/en-us/powershell/module/az.storage/get-azstoragefileserviceproperty
4. https://learn.microsoft.com/en-us/powershell/module/az.storage/update-azstoragefileserviceproperty
5. https://learn.microsoft.com/en-us/azure/storage/files/storage-files-prevent-file-share-deletion

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