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Monitor the Total Number of Subscription Owners

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Risk Level: Medium (should be achieved)
Rule ID: SecurityCenter-022

Ensure that the total number of subscription owners created for your Microsoft Azure account subscriptions is being monitored by the Microsoft Defender for Cloud service. Trend Cloud One™ – Conformity recommends designating up to 3 subscription owners in order to reduce the potential for security breaches by one or more compromised owners.

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

Security

As a security best practice, a maximum number of 3 owners should be designated for a Microsoft Azure subscription. By monitoring the number of subscription owners using Microsoft Defender for Cloud, you can enforce these best practices and always maintain a maximum of 3 subscription owners. This should reduce the risk of a compromised owner's account being used to gain access to your subscription.

Audit

To determine if the number of subscription owners is being monitored with Microsoft Defender for Cloud, perform the following operations:

Using Azure Portal

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: A maximum of 3 owners should be designated for your subscription. If the specified parameter is set to Disabled, the total number of Azure account subscription owners is not monitored using Microsoft Defender for Cloud.

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

Using Azure CLI

01 Run account get-access-token command (Windows/macOS/Linux) using custom query filters to determine if the number of subscription owners is being monitored by checking the identityDesignateLessThanOwnersMonitoringEffect 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.identityDesignateLessThanOwnersMonitoringEffect.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 total number of Azure account subscription owners is not monitored using Microsoft Defender for Cloud.

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

Remediation / Resolution

To begin monitoring the total number of Azure subscription owners using the Microsoft Defender for Cloud service, perform the following operations:

Using Azure Portal

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 A maximum of 3 owners should be designated for your subscription parameter dropdown list to enable the monitoring of maximum subscription owners in the selected Azure account 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

01 Define the configuration parameters for the account get-access-tokencommand, where the identityDesignateLessThanOwnersMonitoringEffect parameter is enabled to turn on the monitoring feature. Save the configuration document to a JSON file named enable-subscription-owners-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":{
        "identityDesignateLessThanOwnersMonitoringEffect":{
           "value":"AuditIfNotExists"
        }
     }
  },
  "id":"/subscriptions//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-subscription-owners-monitoring.json file), to enable the monitoring of maximum subscription owners within the current Azure account 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-subscription-owners-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": {
      "identityDesignateLessThanOwnersMonitoringEffect": {
        "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 Mar 27, 2020

Related SecurityCenter rules