Cross-tenant Access Settings Organization Added

// Tenants IDs can be found by navigating to Azure Active Directory then from menu on the left, select External Identities, then from menu on the left, select Cross-tenant access settings and from the list shown of Tenants
let ExpectedTenantIDs = dynamic(["List of expected tenant IDs","Tenant ID 2"]);
AuditLogs
| where OperationName has "Add a partner to cross-tenant access setting"
| extend InitiatedByActionUserInformation = iff(isnotempty(InitiatedBy.user.userPrincipalName), InitiatedBy.user.userPrincipalName, InitiatedBy.app.displayName)
| extend InitiatedByIPAdress = InitiatedBy.user.ipAddress
| mv-apply TargetResource = TargetResources on
  (
      where TargetResource.type =~ "Policy"
      | extend Properties = TargetResource.modifiedProperties
  )
| mv-apply Property = Properties on
  (
      where Property.displayName =~ "tenantId"
      | extend ExtTenantIDAdded = trim('"',tostring(Property.newValue))
  )
| where ExtTenantIDAdded !in (ExpectedTenantIDs)
| extend Name = tostring(split(InitiatedByActionUserInformation,'@',0)[0]), UPNSuffix = tostring(split(InitiatedByActionUserInformation,'@',1)[0])

OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Microsoft Entra ID/Analytic Rules/Cross-tenantAccessSettingsOrganizationAdded.yaml
entityMappings:
- fieldMappings:
  - identifier: Name
    columnName: Name
  - identifier: UPNSuffix
    columnName: UPNSuffix
  entityType: Account
- fieldMappings:
  - identifier: Address
    columnName: InitiatedByIPAdress
  entityType: IP
kind: Scheduled
query: |
  // Tenants IDs can be found by navigating to Azure Active Directory then from menu on the left, select External Identities, then from menu on the left, select Cross-tenant access settings and from the list shown of Tenants
  let ExpectedTenantIDs = dynamic(["List of expected tenant IDs","Tenant ID 2"]);
  AuditLogs
  | where OperationName has "Add a partner to cross-tenant access setting"
  | extend InitiatedByActionUserInformation = iff(isnotempty(InitiatedBy.user.userPrincipalName), InitiatedBy.user.userPrincipalName, InitiatedBy.app.displayName)
  | extend InitiatedByIPAdress = InitiatedBy.user.ipAddress
  | mv-apply TargetResource = TargetResources on
    (
        where TargetResource.type =~ "Policy"
        | extend Properties = TargetResource.modifiedProperties
    )
  | mv-apply Property = Properties on
    (
        where Property.displayName =~ "tenantId"
        | extend ExtTenantIDAdded = trim('"',tostring(Property.newValue))
    )
  | where ExtTenantIDAdded !in (ExpectedTenantIDs)
  | extend Name = tostring(split(InitiatedByActionUserInformation,'@',0)[0]), UPNSuffix = tostring(split(InitiatedByActionUserInformation,'@',1)[0])  
triggerOperator: gt
version: 1.0.2
queryPeriod: 2d
name: Cross-tenant Access Settings Organization Added
severity: Medium
relevantTechniques:
- T1078.004
- T1136.003
- T1087.004
requiredDataConnectors:
- dataTypes:
  - AuditLogs
  connectorId: AzureActiveDirectory
triggerThreshold: 0
tactics:
- InitialAccess
- Persistence
- Discovery
queryFrequency: 2d
id: 757e6a79-6d23-4ae6-9845-4dac170656b5
status: Available
description: |
    'Organizations are added in the Cross-tenant Access Settings to control communication inbound or outbound for users and applications. This detection notifies when an Organization is added other than the list that is supposed to exist from the Microsoft Entra ID Cross-tenant Access Settings.'

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "workspace": {
      "type": "String"
    }
  },
  "resources": [
    {
      "apiVersion": "2023-02-01-preview",
      "id": "[concat(resourceId('Microsoft.OperationalInsights/workspaces/providers', parameters('workspace'), 'Microsoft.SecurityInsights'),'/alertRules/757e6a79-6d23-4ae6-9845-4dac170656b5')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/757e6a79-6d23-4ae6-9845-4dac170656b5')]",
      "properties": {
        "alertRuleTemplateName": "757e6a79-6d23-4ae6-9845-4dac170656b5",
        "customDetails": null,
        "description": "'Organizations are added in the Cross-tenant Access Settings to control communication inbound or outbound for users and applications. This detection notifies when an Organization is added other than the list that is supposed to exist from the Microsoft Entra ID Cross-tenant Access Settings.'\n",
        "displayName": "Cross-tenant Access Settings Organization Added",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "Name",
                "identifier": "Name"
              },
              {
                "columnName": "UPNSuffix",
                "identifier": "UPNSuffix"
              }
            ]
          },
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "InitiatedByIPAdress",
                "identifier": "Address"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Microsoft Entra ID/Analytic Rules/Cross-tenantAccessSettingsOrganizationAdded.yaml",
        "query": "// Tenants IDs can be found by navigating to Azure Active Directory then from menu on the left, select External Identities, then from menu on the left, select Cross-tenant access settings and from the list shown of Tenants\nlet ExpectedTenantIDs = dynamic([\"List of expected tenant IDs\",\"Tenant ID 2\"]);\nAuditLogs\n| where OperationName has \"Add a partner to cross-tenant access setting\"\n| extend InitiatedByActionUserInformation = iff(isnotempty(InitiatedBy.user.userPrincipalName), InitiatedBy.user.userPrincipalName, InitiatedBy.app.displayName)\n| extend InitiatedByIPAdress = InitiatedBy.user.ipAddress\n| mv-apply TargetResource = TargetResources on\n  (\n      where TargetResource.type =~ \"Policy\"\n      | extend Properties = TargetResource.modifiedProperties\n  )\n| mv-apply Property = Properties on\n  (\n      where Property.displayName =~ \"tenantId\"\n      | extend ExtTenantIDAdded = trim('\"',tostring(Property.newValue))\n  )\n| where ExtTenantIDAdded !in (ExpectedTenantIDs)\n| extend Name = tostring(split(InitiatedByActionUserInformation,'@',0)[0]), UPNSuffix = tostring(split(InitiatedByActionUserInformation,'@',1)[0])\n",
        "queryFrequency": "P2D",
        "queryPeriod": "P2D",
        "severity": "Medium",
        "status": "Available",
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "Discovery",
          "InitialAccess",
          "Persistence"
        ],
        "techniques": [
          "T1078",
          "T1087",
          "T1136"
        ],
        "templateVersion": "1.0.2",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}