Corelight - SMTP Email containing NON Ascii Characters within the Subject

corelight_smtp
| where subject hasprefix @'\=?utf-16'
| mv-expand to_recipient = todynamic(to_) to typeof(string)
| summarize recipients = dcount(to_recipient)
| extend k = 1
| join (corelight_smtp
        | where subject hasprefix @'\=?utf-16'
        | mv-expand to_recipient = todynamic(to_) to typeof(string)
        | summarize by to_recipient
        | extend k = 1) on k
| where recipients > 1

name: Corelight - SMTP Email containing NON Ascii Characters within the Subject
triggerOperator: gt
query: |
  corelight_smtp
  | where subject hasprefix @'\=?utf-16'
  | mv-expand to_recipient = todynamic(to_) to typeof(string)
  | summarize recipients = dcount(to_recipient)
  | extend k = 1
  | join (corelight_smtp
          | where subject hasprefix @'\=?utf-16'
          | mv-expand to_recipient = todynamic(to_) to typeof(string)
          | summarize by to_recipient
          | extend k = 1) on k
  | where recipients > 1
queryFrequency: 1h
description: |
  'Detects where an emails contain non ascii characters within the Subject.'
id: 50c61708-9824-46f3-87cf-22490796fae2
triggerThreshold: 0
queryPeriod: 1h
version: 2.2.0
kind: Scheduled
status: Available
severity: Low
requiredDataConnectors:
- connectorId: Corelight
  dataTypes:
  - corelight_smtp
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Corelight/Analytic%20Rules/CorelightSMTPEmailSubjectNonAsciiCharacters.yaml
relevantTechniques:
- T1566
tactics:
- InitialAccess
entityMappings:
- fieldMappings:
  - identifier: Recipient
    columnName: to_recipient
  entityType: MailMessage

{
  "$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/50c61708-9824-46f3-87cf-22490796fae2')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/50c61708-9824-46f3-87cf-22490796fae2')]",
      "properties": {
        "alertRuleTemplateName": "50c61708-9824-46f3-87cf-22490796fae2",
        "customDetails": null,
        "description": "'Detects where an emails contain non ascii characters within the Subject.'\n",
        "displayName": "Corelight - SMTP Email containing NON Ascii Characters within the Subject",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "MailMessage",
            "fieldMappings": [
              {
                "columnName": "to_recipient",
                "identifier": "Recipient"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Corelight/Analytic%20Rules/CorelightSMTPEmailSubjectNonAsciiCharacters.yaml",
        "query": "corelight_smtp\n| where subject hasprefix @'\\=?utf-16'\n| mv-expand to_recipient = todynamic(to_) to typeof(string)\n| summarize recipients = dcount(to_recipient)\n| extend k = 1\n| join (corelight_smtp\n        | where subject hasprefix @'\\=?utf-16'\n        | mv-expand to_recipient = todynamic(to_) to typeof(string)\n        | summarize by to_recipient\n        | extend k = 1) on k\n| where recipients > 1\n",
        "queryFrequency": "PT1H",
        "queryPeriod": "PT1H",
        "severity": "Low",
        "status": "Available",
        "subTechniques": [],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "InitialAccess"
        ],
        "techniques": [
          "T1566"
        ],
        "templateVersion": "2.2.0",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}