Guest Users Invited to Tenant by New Inviters | Microsoft Sentinel Analytic Rules

Back


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	1.1.1
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 InitiatingUserPrincipalName = tostring(parse_json(tostring(InitiatedBy.user)).userPrincipalName)
  | where isnotempty(InitiatingUserPrincipalName)
  | summarize by InitiatingUserPrincipalName);
  AuditLogs
  | where TimeGenerated > ago(1d)
  | where OperationName =~ "Invite external user"
  | where Result =~ "success"
  | extend InitiatingUserPrincipalName = tostring(parse_json(tostring(InitiatedBy.user)).userPrincipalName)
  | extend InitiatingAadUserId = tostring(InitiatedBy.user.id)
  | extend InitiatingIPAddress = tostring(InitiatedBy.user.ipAddress)
  | where isnotempty(InitiatingUserPrincipalName) and InitiatingUserPrincipalName !in (inviting_users)
  | extend TargetUserPrincipalName = tostring(TargetResources[0].userPrincipalName)
  | extend TargetAadUserId = tostring(TargetResources[0].id)
  | extend invitingUser = InitiatingUserPrincipalName, invitedUserPrincipalName = TargetUserPrincipalName
  | extend InitiatingAccountName = tostring(split(InitiatingUserPrincipalName, "@")[0]), InitiatingAccountUPNSuffix = tostring(split(InitiatingUserPrincipalName, "@")[1])
  | extend TargetAccountName = tostring(split(TargetUserPrincipalName, "@")[0]), TargetAccountUPNSuffix = tostring(split(TargetUserPrincipalName, "@")[1])
  | project-reorder TimeGenerated, OperationName, Result, TargetUserPrincipalName, TargetAadUserId, InitiatingUserPrincipalName, InitiatingAadUserId, InitiatingIPAddress

YAML

entityMappings:
- entityType: Account
  fieldMappings:
  - columnName: InitiatingUserPrincipalName
    identifier: FullName
  - columnName: InitiatingAccountName
    identifier: Name
  - columnName: InitiatingAccountUPNSuffix
    identifier: UPNSuffix
- entityType: Account
  fieldMappings:
  - columnName: TargetUserPrincipalName
    identifier: FullName
  - columnName: TargetAccountName
    identifier: Name
  - columnName: TargetAccountUPNSuffix
    identifier: UPNSuffix
- entityType: Account
  fieldMappings:
  - columnName: InitiatingAadUserId
    identifier: AadUserId
- entityType: Account
  fieldMappings:
  - columnName: TargetAadUserId
    identifier: AadUserId
- entityType: IP
  fieldMappings:
  - columnName: InitiatingIPAddress
    identifier: Address
query: |
  let inviting_users = (AuditLogs
    | where TimeGenerated between(ago(14d)..ago(1d))
    | where OperationName =~ "Invite external user"
    | where Result =~ "success"
    | extend InitiatingUserPrincipalName = tostring(parse_json(tostring(InitiatedBy.user)).userPrincipalName)
    | where isnotempty(InitiatingUserPrincipalName)
    | summarize by InitiatingUserPrincipalName);
    AuditLogs
    | where TimeGenerated > ago(1d)
    | where OperationName =~ "Invite external user"
    | where Result =~ "success"
    | extend InitiatingUserPrincipalName = tostring(parse_json(tostring(InitiatedBy.user)).userPrincipalName)
    | extend InitiatingAadUserId = tostring(InitiatedBy.user.id)
    | extend InitiatingIPAddress = tostring(InitiatedBy.user.ipAddress)
    | where isnotempty(InitiatingUserPrincipalName) and InitiatingUserPrincipalName !in (inviting_users)
    | extend TargetUserPrincipalName = tostring(TargetResources[0].userPrincipalName)
    | extend TargetAadUserId = tostring(TargetResources[0].id)
    | extend invitingUser = InitiatingUserPrincipalName, invitedUserPrincipalName = TargetUserPrincipalName
    | extend InitiatingAccountName = tostring(split(InitiatingUserPrincipalName, "@")[0]), InitiatingAccountUPNSuffix = tostring(split(InitiatingUserPrincipalName, "@")[1])
    | extend TargetAccountName = tostring(split(TargetUserPrincipalName, "@")[0]), TargetAccountUPNSuffix = tostring(split(TargetUserPrincipalName, "@")[1])
    | project-reorder TimeGenerated, OperationName, Result, TargetUserPrincipalName, TargetAadUserId, InitiatingUserPrincipalName, InitiatingAadUserId, InitiatingIPAddress
metadata:
  categories:
    domains:
    - Security - Others
    - Identity
  source:
    kind: Community
  author:
    name: Microsoft Security Research
  support:
    tier: Community
tags:
- AADSecOpsGuide
queryFrequency: 1d
id: 572e75ef-5147-49d9-9d65-13f2ed1e3a86
version: 1.1.1
severity: Medium
relevantTechniques:
- T1078.004
name: Guest Users Invited to Tenant by New Inviters
kind: Scheduled
tactics:
- Persistence
requiredDataConnectors:
- dataTypes:
  - AuditLogs
  connectorId: AzureActiveDirectory
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'
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Detections/AuditLogs/GuestUsersInvitedtoTenantbyNewInviters.yaml
triggerOperator: gt
triggerThreshold: 0
queryPeriod: 14d

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/572e75ef-5147-49d9-9d65-13f2ed1e3a86')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/572e75ef-5147-49d9-9d65-13f2ed1e3a86')]",
      "properties": {
        "alertRuleTemplateName": "572e75ef-5147-49d9-9d65-13f2ed1e3a86",
        "customDetails": null,
        "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",
        "displayName": "Guest Users Invited to Tenant by New Inviters",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "InitiatingUserPrincipalName",
                "identifier": "FullName"
              },
              {
                "columnName": "InitiatingAccountName",
                "identifier": "Name"
              },
              {
                "columnName": "InitiatingAccountUPNSuffix",
                "identifier": "UPNSuffix"
              }
            ]
          },
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "TargetUserPrincipalName",
                "identifier": "FullName"
              },
              {
                "columnName": "TargetAccountName",
                "identifier": "Name"
              },
              {
                "columnName": "TargetAccountUPNSuffix",
                "identifier": "UPNSuffix"
              }
            ]
          },
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "InitiatingAadUserId",
                "identifier": "AadUserId"
              }
            ]
          },
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "TargetAadUserId",
                "identifier": "AadUserId"
              }
            ]
          },
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "InitiatingIPAddress",
                "identifier": "Address"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Detections/AuditLogs/GuestUsersInvitedtoTenantbyNewInviters.yaml",
        "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 InitiatingUserPrincipalName = tostring(parse_json(tostring(InitiatedBy.user)).userPrincipalName)\n  | where isnotempty(InitiatingUserPrincipalName)\n  | summarize by InitiatingUserPrincipalName);\n  AuditLogs\n  | where TimeGenerated > ago(1d)\n  | where OperationName =~ \"Invite external user\"\n  | where Result =~ \"success\"\n  | extend InitiatingUserPrincipalName = tostring(parse_json(tostring(InitiatedBy.user)).userPrincipalName)\n  | extend InitiatingAadUserId = tostring(InitiatedBy.user.id)\n  | extend InitiatingIPAddress = tostring(InitiatedBy.user.ipAddress)\n  | where isnotempty(InitiatingUserPrincipalName) and InitiatingUserPrincipalName !in (inviting_users)\n  | extend TargetUserPrincipalName = tostring(TargetResources[0].userPrincipalName)\n  | extend TargetAadUserId = tostring(TargetResources[0].id)\n  | extend invitingUser = InitiatingUserPrincipalName, invitedUserPrincipalName = TargetUserPrincipalName\n  | extend InitiatingAccountName = tostring(split(InitiatingUserPrincipalName, \"@\")[0]), InitiatingAccountUPNSuffix = tostring(split(InitiatingUserPrincipalName, \"@\")[1])\n  | extend TargetAccountName = tostring(split(TargetUserPrincipalName, \"@\")[0]), TargetAccountUPNSuffix = tostring(split(TargetUserPrincipalName, \"@\")[1])\n  | project-reorder TimeGenerated, OperationName, Result, TargetUserPrincipalName, TargetAadUserId, InitiatingUserPrincipalName, InitiatingAadUserId, InitiatingIPAddress\n",
        "queryFrequency": "P1D",
        "queryPeriod": "P14D",
        "severity": "Medium",
        "subTechniques": [
          "T1078.004"
        ],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "Persistence"
        ],
        "tags": [
          "AADSecOpsGuide"
        ],
        "techniques": [
          "T1078"
        ],
        "templateVersion": "1.1.1",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}