External User Access Enabled

ZoomLogs
| where Event =~ "account.settings_updated"
| extend EnforceLogin = columnifexists("payload_object_settings_schedule_meeting_enfore_login_b", "")
| extend EnforceLoginDomain = columnifexists("payload_object_settings_schedule_meeting_enfore_login_b", "")
| extend GuestAlerts = columnifexists("payload_object_settings_in_meeting_alert_guest_join_b", "")
| where EnforceLogin == 'false' or EnforceLoginDomain == 'false' or GuestAlerts == 'false'
| extend SettingChanged = case(EnforceLogin == 'false' and EnforceLoginDomain == 'false' and GuestAlerts == 'false', "All settings changed",
                            EnforceLogin == 'false' and EnforceLoginDomain == 'false', "Enforced Logons and Restricted Domains Changed",
                            EnforceLoginDomain == 'false' and GuestAlerts == 'false', "Enforced Domains Changed",
                            EnforceLoginDomain == 'false', "Enfored Domains Changed",
                            GuestAlerts == 'false', "Guest Join Alerts Changed",
                            EnforceLogin == 'false', "Enforced Logins Changed",
                            "No Changes")
| extend AccountName = tostring(split(User, "@")[0]), AccountUPNSuffix = tostring(split(User, "@")[1])

relevantTechniques:
- T1098
- T1556
queryPeriod: 1d
tactics:
- CredentialAccess
- Persistence
requiredDataConnectors: []
triggerThreshold: 0
entityMappings:
- fieldMappings:
  - identifier: FullName
    columnName: User
  - identifier: Name
    columnName: AccountName
  - identifier: UPNSuffix
    columnName: AccountUPNSuffix
  entityType: Account
name: External User Access Enabled
query: |
  ZoomLogs
  | where Event =~ "account.settings_updated"
  | extend EnforceLogin = columnifexists("payload_object_settings_schedule_meeting_enfore_login_b", "")
  | extend EnforceLoginDomain = columnifexists("payload_object_settings_schedule_meeting_enfore_login_b", "")
  | extend GuestAlerts = columnifexists("payload_object_settings_in_meeting_alert_guest_join_b", "")
  | where EnforceLogin == 'false' or EnforceLoginDomain == 'false' or GuestAlerts == 'false'
  | extend SettingChanged = case(EnforceLogin == 'false' and EnforceLoginDomain == 'false' and GuestAlerts == 'false', "All settings changed",
                              EnforceLogin == 'false' and EnforceLoginDomain == 'false', "Enforced Logons and Restricted Domains Changed",
                              EnforceLoginDomain == 'false' and GuestAlerts == 'false', "Enforced Domains Changed",
                              EnforceLoginDomain == 'false', "Enfored Domains Changed",
                              GuestAlerts == 'false', "Guest Join Alerts Changed",
                              EnforceLogin == 'false', "Enforced Logins Changed",
                              "No Changes")
  | extend AccountName = tostring(split(User, "@")[0]), AccountUPNSuffix = tostring(split(User, "@")[1])  
queryFrequency: 1d
id: 8e267e91-6bda-4b3c-bf68-9f5cbdd103a3
severity: Low
description: |
    'This alerts when the account setting is changed to allow either external domain access or anonymous access to meetings.'
metadata:
  source:
    kind: Community
  categories:
    domains:
    - Security - Others
    - Identity
  support:
    tier: Community
  author:
    name: Microsoft Security Research
version: 1.0.4
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Detections/ZoomLogs/ExternalUserAccess.yaml
kind: Scheduled
triggerOperator: gt

{
  "$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/8e267e91-6bda-4b3c-bf68-9f5cbdd103a3')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/8e267e91-6bda-4b3c-bf68-9f5cbdd103a3')]",
      "properties": {
        "alertRuleTemplateName": "8e267e91-6bda-4b3c-bf68-9f5cbdd103a3",
        "customDetails": null,
        "description": "'This alerts when the account setting is changed to allow either external domain access or anonymous access to meetings.'\n",
        "displayName": "External User Access Enabled",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "User",
                "identifier": "FullName"
              },
              {
                "columnName": "AccountName",
                "identifier": "Name"
              },
              {
                "columnName": "AccountUPNSuffix",
                "identifier": "UPNSuffix"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Detections/ZoomLogs/ExternalUserAccess.yaml",
        "query": "ZoomLogs\n| where Event =~ \"account.settings_updated\"\n| extend EnforceLogin = columnifexists(\"payload_object_settings_schedule_meeting_enfore_login_b\", \"\")\n| extend EnforceLoginDomain = columnifexists(\"payload_object_settings_schedule_meeting_enfore_login_b\", \"\")\n| extend GuestAlerts = columnifexists(\"payload_object_settings_in_meeting_alert_guest_join_b\", \"\")\n| where EnforceLogin == 'false' or EnforceLoginDomain == 'false' or GuestAlerts == 'false'\n| extend SettingChanged = case(EnforceLogin == 'false' and EnforceLoginDomain == 'false' and GuestAlerts == 'false', \"All settings changed\",\n                            EnforceLogin == 'false' and EnforceLoginDomain == 'false', \"Enforced Logons and Restricted Domains Changed\",\n                            EnforceLoginDomain == 'false' and GuestAlerts == 'false', \"Enforced Domains Changed\",\n                            EnforceLoginDomain == 'false', \"Enfored Domains Changed\",\n                            GuestAlerts == 'false', \"Guest Join Alerts Changed\",\n                            EnforceLogin == 'false', \"Enforced Logins Changed\",\n                            \"No Changes\")\n| extend AccountName = tostring(split(User, \"@\")[0]), AccountUPNSuffix = tostring(split(User, \"@\")[1])\n",
        "queryFrequency": "P1D",
        "queryPeriod": "P1D",
        "severity": "Low",
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "CredentialAccess",
          "Persistence"
        ],
        "techniques": [
          "T1098",
          "T1556"
        ],
        "templateVersion": "1.0.4",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}