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Monitor Disk Encryption

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Risk Level: Medium (should be achieved)
Rule ID: SecurityCenter-006

Ensure that disk encryption monitoring is enabled within Microsoft Defender for Cloud settings in order to detect if your Azure virtual machines (Windows and Linux) have disk encryption enabled.

This rule resolution is part of the Conformity Security & Compliance tool for Azure.

Security

By default, the OS and the data disks associated with a virtual machine are encrypted-at-rest using platform-managed keys. However, temp disks, data caches, and data flowing between compute and storage aren't encrypted. When working with production and business critical data it is highly recommended to implement encryption in order to protect all your data from unauthorized access and fulfill compliance requirements for data-at-rest encryption in your organization. Microsoft Defender for Cloud disk encryption monitoring identifies non-compliant virtual machines (VMs) and recommends enabling full disk encryption in order to enhance data protection.

Audit

To determine if disk encryption monitoring is enabled within the Microsoft Defender for Cloud security policy, perform the following operations:

Using Azure Console

01 Sign in to the Microsoft Azure Portal.

02 Navigate to Microsoft Defender for Cloud blade at https://portal.azure.com/#blade/Microsoft_Azure_Security/SecurityMenuBlade/0.

03 In the main navigation panel, under Management, choose Environment settings.

04 Click on the name (link) of the Azure subscription that you want to examine.

05 In the navigation panel, under Policy settings, choose Security policy.

06 In the Default initiative section, click on the name of the default initiative enabled for the selected subscription (i.e. ASC Default (subscription: <subscription-id>)).

07 Choose the Parameters tab, uncheck Only show parameters that need input or review, and search for the following parameter: Virtual machines should encrypt temp disks, caches, and data flows between Compute and Storage resources If the specified parameter is set to Disabled, the monitoring of virtual machine disk encryption is not enabled within the selected Azure subscription.

08 Repeat steps no. 4 – 7 for each Microsoft Azure subscription created within your Azure account.

Using Azure CLI and PowerShell

01 Run account get-access-token command (Windows/macOS/Linux) using custom query filters to determine if the monitoring of VM disk encryption is enabled within the current Azure subscription by checking the diskEncryptionMonitoringEffect configuration parameter value: 

az account get-access-token
  --query "{subscription:subscription,accessToken:accessToken}"
  --out tsv | xargs -L1 bash -c 'curl -X GET -H "Authorization: Bearer $1" -H "Content-Type: application/json" https://management.azure.com/subscriptions/$0/providers/Microsoft.Authorization/policyAssignments/SecurityCenterBuiltIn?api-version=2018-05-01' | jq 'select(.name=="SecurityCenterBuiltIn")'|jq '.properties.parameters.diskEncryptionMonitoringEffect.value'

02 The command output should return the requested parameter value: 

"Disabled"

If the account get-access-token command output returns "Disabled", as shown in the output example above, the disk encryption monitoring for Azure virtual machines (VMs) is not enabled within the current subscription.

03 Repeat steps no. 1 and 2 for each Microsoft Azure subscription available in your Azure cloud account.

Remediation / Resolution

To enable the disk encryption monitoring for Azure virtual machines within the Microsoft Defender for Cloud security policy, perform the following operations:

Using Azure Console

01 Sign in to the Microsoft Azure Portal.

02 Navigate to Microsoft Defender for Cloud blade at https://portal.azure.com/#blade/Microsoft_Azure_Security/SecurityMenuBlade/0.

03 In the main navigation panel, under Management, choose Environment settings.

04 Click on the name (link) of the Azure subscription that you want to access.

05 In the navigation panel, under Policy settings, choose Security policy.

06 In the Default initiative section, click on the name of the default initiative enabled for the selected subscription (i.e. ASC Default (subscription: <subscription-id>)).

07 Choose the Parameters tab and uncheck the Only show parameters that need input or review checkbox to list all the initiative parameters.

08 Select AuditIfNotExists from the Virtual machines should encrypt temp disks, caches, and data flows between Compute and Storage resources parameter dropdown list to enable the disk encryption monitoring feature for the virtual machines provisioned within the selected Azure subscription.

09 Select Review + save to review the configuration changes, then choose Save to apply the new changes. If the operation is successful, the following confirmation message should be displayed: "Updating policy assignment succeeded".

10 Repeat steps no. 4 – 9 for each Microsoft Azure subscription available within your Azure account.

Using Azure CLI and PowerShell

01 Define the configuration parameters for the account get-access-token command, where the diskEncryptionMonitoringEffect parameter is enabled to turn on the monitoring feature. Save the configuration document to a JSON file named enable-vm-disk-encryption-monitoring.json and replace the highlighted details, i.e. <azure-subscription-id> and <policy-definition-id>, with your own Azure account subscription details: 

{
  "properties":{
     "displayName":"ASC Default (subscription: <azure-subscription-id>)",
     "policyDefinitionId":"/providers/Microsoft.Authorization/policySetDefinitions/<policy-definition-id>",
     "scope":"/subscriptions/<azure-subscription-id>",
     "parameters":{
        "diskEncryptionMonitoringEffect":{
           "value":"AuditIfNotExists"
        }
     }
  },
  "id":"/subscriptions/<azure-subscription-id>/providers/Microsoft.Authorization/policyAssignments/SecurityCenterBuiltIn",
  "type":"Microsoft.Authorization/policyAssignments",
  "name":"SecurityCenterBuiltIn",
  "location":"eastus"
}

02 Run account get-access-token command (Windows/macOS/Linux) using the configuration document defined at the previous step (i.e. enable-vm-disk-encryption-monitoring.json file), to enable the disk encryption monitoring feature for the virtual machines provisioned in the selected Azure subscription: 

az account get-access-token
  --query "{subscription:subscription,accessToken:accessToken}"
  --out tsv | xargs -L1 bash -c 'curl -X PUT -H "Authorization: Bearer $1" -H "Content-Type: application/json" https://management.azure.com/subscriptions/$0/providers/Microsoft.Authorization/policyAssignments/SecurityCenterBuiltIn?api-version=2018-05-01 -d@"enable-vm-disk-encryption-monitoring.json"'

03 The command output should return information about the modified configuration parameter: 

{
  "sku": {
    "name": "A0",
    "tier": "Free"
  },
  "properties": {
    "displayName": "ASC Default (subscription: abcdabcd-1234-1234-1234-abcdabcdabcd)",
    "policyDefinitionId": "/providers/Microsoft.Authorization/policySetDefinitions/1234abcd-1234-1234-1234-abcd1234abcd",
    "scope": "/subscriptions/abcdabcd-1234-1234-1234-abcdabcdabcd",
    "parameters": {
      "diskEncryptionMonitoringEffect": {
        "value": "AuditIfNotExists"
      }
    },
    "metadata": {
      "createdBy": "abcdabcd-1234-1234-1234-abcdabcdabcd",
      "createdOn": "2019-05-17T15:38:40.3473931Z",
      "updatedBy": "1234abcd-1234-1234-1234-abcd1234abcd",
      "updatedOn": "2022-02-01T21:22:40.7422203Z"
    }
  },
  "id": "/subscriptions/abcdabcd-1234-1234-1234-abcdabcdabcd/providers/Microsoft.Authorization/policyAssignments/SecurityCenterBuiltIn",
  "type": "Microsoft.Authorization/policyAssignments",
  "name": "SecurityCenterBuiltIn",
  "location": "eastus"
}

04 Repeat steps no. 1 – 3 for each Microsoft Azure subscription available in your Azure cloud account.

References

Publication date May 21, 2019

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Monitor Disk Encryption

Risk Level: Medium