Guest Users Invited to Tenant by New Inviters

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Id	572e75ef-5147-49d9-9d65-13f2ed1e3a86
Rulename	Guest Users Invited to Tenant by New Inviters
Description	Detects when a Guest User is added by a user account that has not been seen adding a guest in the previous 14 days. Monitoring guest accounts and the access they are provided is important to detect potential account abuse. Accounts added should be investigated to ensure the activity was legitimate. Ref: https://docs.microsoft.com/azure/active-directory/fundamentals/security-operations-user-accounts#monitoring-for-failed-unusual-sign-ins
Severity	Medium
Tactics	Persistence
Techniques	T1078.004
Required data connectors	AzureActiveDirectory
Kind	Scheduled
Query frequency	1d
Query period	14d
Trigger threshold	0
Trigger operator	gt
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Detections/AuditLogs/GuestUsersInvitedtoTenantbyNewInviters.yaml
Version	1.0.1
Arm template	572e75ef-5147-49d9-9d65-13f2ed1e3a86.json

KQL

let inviting_users = (AuditLogs
  | where TimeGenerated between(ago(14d)..ago(1d))
  | where OperationName =~ "Invite external user"
  | where Result =~ "success"
  | extend invitingUser = tostring(parse_json(tostring(InitiatedBy.user)).userPrincipalName)
  | where isnotempty(invitingUser)
  | summarize by invitingUser);
  AuditLogs
  | where TimeGenerated > ago(1d)
  | where OperationName =~ "Invite external user"
  | where Result =~ "success"
  | extend invitingUser = tostring(parse_json(tostring(InitiatedBy.user)).userPrincipalName)
  | where isnotempty(invitingUser) and invitingUser !in (inviting_users)
  | extend invitedUserPrincipalName = tostring(TargetResources[0].userPrincipalName)
  | extend ipAddress = tostring(parse_json(tostring(InitiatedBy.user)).ipAddress)

YAML

metadata:
  author:
    name: Pete Bryan
  support:
    tier: Community
  source:
    kind: Community
  categories:
    domains:
    - Security - Others
    - Identity
severity: Medium
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Detections/AuditLogs/GuestUsersInvitedtoTenantbyNewInviters.yaml
description: |
  'Detects when a Guest User is added by a user account that has not been seen adding a guest in the previous 14 days.
    Monitoring guest accounts and the access they are provided is important to detect potential account abuse.
    Accounts added should be investigated to ensure the activity was legitimate.
    Ref: https://docs.microsoft.com/azure/active-directory/fundamentals/security-operations-user-accounts#monitoring-for-failed-unusual-sign-ins'  
tags:
- AADSecOpsGuide
triggerOperator: gt
queryPeriod: 14d
requiredDataConnectors:
- dataTypes:
  - AuditLogs
  connectorId: AzureActiveDirectory
queryFrequency: 1d
triggerThreshold: 0
tactics:
- Persistence
query: |
  let inviting_users = (AuditLogs
    | where TimeGenerated between(ago(14d)..ago(1d))
    | where OperationName =~ "Invite external user"
    | where Result =~ "success"
    | extend invitingUser = tostring(parse_json(tostring(InitiatedBy.user)).userPrincipalName)
    | where isnotempty(invitingUser)
    | summarize by invitingUser);
    AuditLogs
    | where TimeGenerated > ago(1d)
    | where OperationName =~ "Invite external user"
    | where Result =~ "success"
    | extend invitingUser = tostring(parse_json(tostring(InitiatedBy.user)).userPrincipalName)
    | where isnotempty(invitingUser) and invitingUser !in (inviting_users)
    | extend invitedUserPrincipalName = tostring(TargetResources[0].userPrincipalName)
    | extend ipAddress = tostring(parse_json(tostring(InitiatedBy.user)).ipAddress)  
kind: Scheduled
relevantTechniques:
- T1078.004
version: 1.0.1
id: 572e75ef-5147-49d9-9d65-13f2ed1e3a86
entityMappings:
- fieldMappings:
  - columnName: invitingUser
    identifier: FullName
  entityType: Account
- fieldMappings:
  - columnName: invitedUserPrincipalName
    identifier: FullName
  entityType: Account
- fieldMappings:
  - columnName: ipAddress
    identifier: Address
  entityType: IP
name: Guest Users Invited to Tenant by New Inviters

ARM

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "workspace": {
      "type": "String"
    }
  },
  "resources": [
    {
      "id": "[concat(resourceId('Microsoft.OperationalInsights/workspaces/providers', parameters('workspace'), 'Microsoft.SecurityInsights'),'/alertRules/572e75ef-5147-49d9-9d65-13f2ed1e3a86')]",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/572e75ef-5147-49d9-9d65-13f2ed1e3a86')]",
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules",
      "kind": "Scheduled",
      "apiVersion": "2022-11-01-preview",
      "properties": {
        "displayName": "Guest Users Invited to Tenant by New Inviters",
        "description": "'Detects when a Guest User is added by a user account that has not been seen adding a guest in the previous 14 days.\n  Monitoring guest accounts and the access they are provided is important to detect potential account abuse.\n  Accounts added should be investigated to ensure the activity was legitimate.\n  Ref: https://docs.microsoft.com/azure/active-directory/fundamentals/security-operations-user-accounts#monitoring-for-failed-unusual-sign-ins'\n",
        "severity": "Medium",
        "enabled": true,
        "query": "let inviting_users = (AuditLogs\n  | where TimeGenerated between(ago(14d)..ago(1d))\n  | where OperationName =~ \"Invite external user\"\n  | where Result =~ \"success\"\n  | extend invitingUser = tostring(parse_json(tostring(InitiatedBy.user)).userPrincipalName)\n  | where isnotempty(invitingUser)\n  | summarize by invitingUser);\n  AuditLogs\n  | where TimeGenerated > ago(1d)\n  | where OperationName =~ \"Invite external user\"\n  | where Result =~ \"success\"\n  | extend invitingUser = tostring(parse_json(tostring(InitiatedBy.user)).userPrincipalName)\n  | where isnotempty(invitingUser) and invitingUser !in (inviting_users)\n  | extend invitedUserPrincipalName = tostring(TargetResources[0].userPrincipalName)\n  | extend ipAddress = tostring(parse_json(tostring(InitiatedBy.user)).ipAddress)\n",
        "queryFrequency": "P1D",
        "queryPeriod": "P14D",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0,
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "Persistence"
        ],
        "techniques": [
          "T1078.004"
        ],
        "alertRuleTemplateName": "572e75ef-5147-49d9-9d65-13f2ed1e3a86",
        "customDetails": null,
        "entityMappings": [
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "invitingUser",
                "identifier": "FullName"
              }
            ]
          },
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "invitedUserPrincipalName",
                "identifier": "FullName"
              }
            ]
          },
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "ipAddress",
                "identifier": "Address"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Detections/AuditLogs/GuestUsersInvitedtoTenantbyNewInviters.yaml",
        "tags": [
          "AADSecOpsGuide"
        ],
        "templateVersion": "1.0.1"
      }
    }
  ]
}