Microsoft Sentinel Analytic Rules
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Corelight - SMTP Email containing NON Ascii Characters within the Subject

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Id50c61708-9824-46f3-87cf-22490796fae2
RulenameCorelight - SMTP Email containing NON Ascii Characters within the Subject
DescriptionDetects where an emails contain non ascii characters within the Subject.
SeverityLow
TacticsInitialAccess
TechniquesT1566
Required data connectorsCorelight
KindScheduled
Query frequency1h
Query period1h
Trigger threshold0
Trigger operatorgt
Source Urihttps://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Corelight/Analytic Rules/CorelightSMTPEmailSubjectNonAsciiCharacters.yaml
Version2.1.0
Arm template50c61708-9824-46f3-87cf-22490796fae2.json
Deploy To Azure
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
kind: Scheduled
tactics:
- InitialAccess
name: Corelight - SMTP Email containing NON Ascii Characters within the Subject
id: 50c61708-9824-46f3-87cf-22490796fae2
queryFrequency: 1h
severity: Low
version: 2.1.0
triggerThreshold: 0
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Corelight/Analytic Rules/CorelightSMTPEmailSubjectNonAsciiCharacters.yaml
queryPeriod: 1h
description: |
    'Detects where an emails contain non ascii characters within the Subject.'
triggerOperator: gt
status: Available
requiredDataConnectors:
- dataTypes:
  - Corelight_v2_smtp
  - corelight_smtp
  connectorId: Corelight
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  
entityMappings:
- entityType: MailMessage
  fieldMappings:
  - columnName: _to
    identifier: Recipient
relevantTechniques:
- T1566
{
  "$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"
    }
  ]
}