Corelight - SMTP Email containing NON Ascii Characters within the Subject

corelight_smtp
| where subject hasprefix  @'\=?utf-16'
| summarize recipients = dcount(_to)
| extend k = 1
| join (corelight_smtp
        | where subject hasprefix  @'\=?utf-16'
        | summarize by _to
        | extend k = 1) on k
| where recipients > 1

relevantTechniques:
- T1566
name: Corelight - SMTP Email containing NON Ascii Characters within the Subject
requiredDataConnectors:
- dataTypes:
  - Corelight_v2_smtp
  - corelight_smtp
  connectorId: Corelight
entityMappings:
- fieldMappings:
  - identifier: Recipient
    columnName: _to
  entityType: MailMessage
triggerThreshold: 0
id: 50c61708-9824-46f3-87cf-22490796fae2
tactics:
- InitialAccess
version: 2.1.0
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Corelight/Analytic Rules/CorelightSMTPEmailSubjectNonAsciiCharacters.yaml
queryPeriod: 1h
kind: Scheduled
queryFrequency: 1h
severity: Low
status: Available
description: |
    'Detects where an emails contain non ascii characters within the Subject.'
query: |
  corelight_smtp
  | where subject hasprefix  @'\=?utf-16'
  | summarize recipients = dcount(_to)
  | extend k = 1
  | join (corelight_smtp
          | where subject hasprefix  @'\=?utf-16'
          | summarize by _to
          | extend k = 1) on k
  | where recipients > 1  
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": "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",
                "identifier": "Recipient"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Corelight/Analytic Rules/CorelightSMTPEmailSubjectNonAsciiCharacters.yaml",
        "query": "corelight_smtp\n| where subject hasprefix  @'\\=?utf-16'\n| summarize recipients = dcount(_to)\n| extend k = 1\n| join (corelight_smtp\n        | where subject hasprefix  @'\\=?utf-16'\n        | summarize by _to\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": "2.1.0",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}