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Monitor System Updates

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Risk Level: Medium (should be achieved)
Rule ID: SecurityCenter-003

Ensure that system updates monitoring is enabled within your Azure cloud account in order to be notified about the security and critical updates released from Microsoft Windows Update or Microsoft Windows Server Update service.

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

Security

When this feature is enabled, it retrieves a daily list of available security and critical updates from Microsoft Windows Update/Microsoft Windows Server Update. The security updates on this list depend on the service configured for that specific Azure virtual machine (VM) and recommends via notifications that the missing updates be applied as soon as possible. This is to ensure that the virtual machine's operating system is running the most recent security updates provided by the software vendor. For Unix/Linux systems, the feature uses the distro-provided package management system to determine packages that have available updates.

Audit

To determine if the system updates 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: System updates should be installed on your machines. If the System updates should be installed on your machines parameter is set to Disabled, the system updates recommendations are not enabled for the Microsoft Azure virtual machines (VMs) provisioned in the selected 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 system updates monitoring is enabled within the current Azure subscription by checking the systemUpdatesMonitoringEffect 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.systemUpdatesMonitoringEffect.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 system updates recommendations are not enabled for the Microsoft Azure virtual machines (VMs) provisioned 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 system updates monitoring and recommendations for your Microsoft Azure virtual machines (VMs), 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 System updates should be installed on your machines parameter dropdown list to enable system updates monitoring and recommendations for your Azure virtual machines (VMs).

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 systemUpdatesMonitoringEffect parameter is enabled to turn on the system monitoring feature. Save the configuration document to a JSON file named enable-system-updates-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":{
        "systemUpdatesMonitoringEffect":{
           "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-system-updates-monitoring.json file), to enable the monitoring/reporting of system updates for your Azure virtual machines (VMs): 

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-system-updates-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": {
      "systemUpdatesMonitoringEffect": {
        "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

Related SecurityCenter rules