New onmicrosoft domain added to tenant

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Id	4f42b94f-b210-42d1-a023-7fa1c51d969f
Rulename	New onmicrosoft domain added to tenant
Description	This detection looks for new onmicrosoft domains being added to a tenant. An attacker who compromises a tenant may register a new onmicrosoft domain in order to masquerade as a service provider for launching phishing campaigns. Domain additions are not a common occurrence and users should validate that the domain was added by a legitimate user, with a legitimate purpose.
Severity	Medium
Tactics	ResourceDevelopment
Techniques	T1585.003
Required data connectors	AzureActiveDirectory
Kind	Scheduled
Query frequency	1h
Query period	1h
Trigger threshold	0
Trigger operator	gt
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Microsoft Entra ID/Analytic Rules/NewOnmicrosoftDomainAdded.yaml
Version	1.0.1
Arm template	4f42b94f-b210-42d1-a023-7fa1c51d969f.json

KQL

AuditLogs
| where AADOperationType == "Add"
| where Result == "success"
| where OperationName in ("Add verified domain", "Add unverified domain")
| extend InitiatedBy = parse_json(InitiatedBy)
| extend InitiatingUser = tostring(InitiatedBy.user.userPrincipalName)
| extend InitiatingAadUserId = tostring(InitiatedBy.user.id)
| extend InitiatingIp = tostring(InitiatedBy.user.ipAddress)
| extend InitiatingApp = tostring(InitiatedBy.app.displayName)
| extend InitiatingSPID = tostring(InitiatedBy.app.servicePrincipalId)
| extend DomainAdded = tostring(TargetResources[0].displayName)
| where DomainAdded has "onmicrosoft"
| extend ActionInitiatedBy = case(isnotempty(InitiatingUser), InitiatingUser, strcat(InitiatingApp, " - ", InitiatingSPID))
| extend UserName = split(InitiatingUser, "@")[0]
| extend UPNSuffix = split(InitiatingUser, "@")[1]
| project-reorder TimeGenerated, OperationName, DomainAdded, ActionInitiatedBy, InitiatingIp

YAML

relevantTechniques:
- T1585.003
name: New onmicrosoft domain added to tenant
requiredDataConnectors:
- dataTypes:
  - AuditLogs
  connectorId: AzureActiveDirectory
entityMappings:
- fieldMappings:
  - identifier: FullName
    columnName: InitiatingUser
  - identifier: Name
    columnName: UserName
  - identifier: UPNSuffix
    columnName: UPNSuffix
  entityType: Account
- fieldMappings:
  - identifier: AadUserId
    columnName: InitiatingAadUserId
  entityType: Account
- fieldMappings:
  - identifier: AadUserId
    columnName: InitiatingSPID
  entityType: Account
- fieldMappings:
  - identifier: Address
    columnName: InitiatingIp
  entityType: IP
- fieldMappings:
  - identifier: DomainName
    columnName: DomainAdded
  entityType: DNS
triggerThreshold: 0
id: 4f42b94f-b210-42d1-a023-7fa1c51d969f
tactics:
- ResourceDevelopment
version: 1.0.1
alertDetailsOverride:
  alertDisplayNameFormat: '{{DomainAdded}} added to tenant by {{ActionInitiatedBy}}'
  alertDescriptionFormat: This detection looks for new onmicrosoft domains being added to a tenant. An attacker who compromises a tenant may register a new onmicrosoft domain in order to masquerade as a service provider for launching phishing accounts. Domain additions are not a common occurrence and users should validate that {{ActionInitiatedBy}} added {{DomainAdded}} with a legitimate purpose.
queryPeriod: 1h
kind: Scheduled
eventGroupingSettings:
  aggregationKind: SingleAlert
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Microsoft Entra ID/Analytic Rules/NewOnmicrosoftDomainAdded.yaml
queryFrequency: 1h
severity: Medium
status: Available
description: |
  'This detection looks for new onmicrosoft domains being added to a tenant. 
  An attacker who compromises a tenant may register a new onmicrosoft domain in order to masquerade as a service provider for launching phishing campaigns.
  Domain additions are not a common occurrence and users should validate that the domain was added by a legitimate user, with a legitimate purpose.'  
query: |
  AuditLogs
  | where AADOperationType == "Add"
  | where Result == "success"
  | where OperationName in ("Add verified domain", "Add unverified domain")
  | extend InitiatedBy = parse_json(InitiatedBy)
  | extend InitiatingUser = tostring(InitiatedBy.user.userPrincipalName)
  | extend InitiatingAadUserId = tostring(InitiatedBy.user.id)
  | extend InitiatingIp = tostring(InitiatedBy.user.ipAddress)
  | extend InitiatingApp = tostring(InitiatedBy.app.displayName)
  | extend InitiatingSPID = tostring(InitiatedBy.app.servicePrincipalId)
  | extend DomainAdded = tostring(TargetResources[0].displayName)
  | where DomainAdded has "onmicrosoft"
  | extend ActionInitiatedBy = case(isnotempty(InitiatingUser), InitiatingUser, strcat(InitiatingApp, " - ", InitiatingSPID))
  | extend UserName = split(InitiatingUser, "@")[0]
  | extend UPNSuffix = split(InitiatingUser, "@")[1]
  | project-reorder TimeGenerated, OperationName, DomainAdded, ActionInitiatedBy, InitiatingIp  
triggerOperator: gt

ARM

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "workspace": {
      "type": "String"
    }
  },
  "resources": [
    {
      "apiVersion": "2024-01-01-preview",
      "id": "[concat(resourceId('Microsoft.OperationalInsights/workspaces/providers', parameters('workspace'), 'Microsoft.SecurityInsights'),'/alertRules/4f42b94f-b210-42d1-a023-7fa1c51d969f')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/4f42b94f-b210-42d1-a023-7fa1c51d969f')]",
      "properties": {
        "alertDetailsOverride": {
          "alertDescriptionFormat": "This detection looks for new onmicrosoft domains being added to a tenant. An attacker who compromises a tenant may register a new onmicrosoft domain in order to masquerade as a service provider for launching phishing accounts. Domain additions are not a common occurrence and users should validate that {{ActionInitiatedBy}} added {{DomainAdded}} with a legitimate purpose.",
          "alertDisplayNameFormat": "{{DomainAdded}} added to tenant by {{ActionInitiatedBy}}"
        },
        "alertRuleTemplateName": "4f42b94f-b210-42d1-a023-7fa1c51d969f",
        "customDetails": null,
        "description": "'This detection looks for new onmicrosoft domains being added to a tenant. \nAn attacker who compromises a tenant may register a new onmicrosoft domain in order to masquerade as a service provider for launching phishing campaigns.\nDomain additions are not a common occurrence and users should validate that the domain was added by a legitimate user, with a legitimate purpose.'\n",
        "displayName": "New onmicrosoft domain added to tenant",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "InitiatingUser",
                "identifier": "FullName"
              },
              {
                "columnName": "UserName",
                "identifier": "Name"
              },
              {
                "columnName": "UPNSuffix",
                "identifier": "UPNSuffix"
              }
            ]
          },
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "InitiatingAadUserId",
                "identifier": "AadUserId"
              }
            ]
          },
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "InitiatingSPID",
                "identifier": "AadUserId"
              }
            ]
          },
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "InitiatingIp",
                "identifier": "Address"
              }
            ]
          },
          {
            "entityType": "DNS",
            "fieldMappings": [
              {
                "columnName": "DomainAdded",
                "identifier": "DomainName"
              }
            ]
          }
        ],
        "eventGroupingSettings": {
          "aggregationKind": "SingleAlert"
        },
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Microsoft Entra ID/Analytic Rules/NewOnmicrosoftDomainAdded.yaml",
        "query": "AuditLogs\n| where AADOperationType == \"Add\"\n| where Result == \"success\"\n| where OperationName in (\"Add verified domain\", \"Add unverified domain\")\n| extend InitiatedBy = parse_json(InitiatedBy)\n| extend InitiatingUser = tostring(InitiatedBy.user.userPrincipalName)\n| extend InitiatingAadUserId = tostring(InitiatedBy.user.id)\n| extend InitiatingIp = tostring(InitiatedBy.user.ipAddress)\n| extend InitiatingApp = tostring(InitiatedBy.app.displayName)\n| extend InitiatingSPID = tostring(InitiatedBy.app.servicePrincipalId)\n| extend DomainAdded = tostring(TargetResources[0].displayName)\n| where DomainAdded has \"onmicrosoft\"\n| extend ActionInitiatedBy = case(isnotempty(InitiatingUser), InitiatingUser, strcat(InitiatingApp, \" - \", InitiatingSPID))\n| extend UserName = split(InitiatingUser, \"@\")[0]\n| extend UPNSuffix = split(InitiatingUser, \"@\")[1]\n| project-reorder TimeGenerated, OperationName, DomainAdded, ActionInitiatedBy, InitiatingIp\n",
        "queryFrequency": "PT1H",
        "queryPeriod": "PT1H",
        "severity": "Medium",
        "status": "Available",
        "subTechniques": [
          "T1585.003"
        ],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "ResourceDevelopment"
        ],
        "techniques": [
          "T1585"
        ],
        "templateVersion": "1.0.1",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}