Corelight - SMTP Email containing NON Ascii Characters within the Subject

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Id	50c61708-9824-46f3-87cf-22490796fae2
Rulename	Corelight - SMTP Email containing NON Ascii Characters within the Subject
Description	Detects where an emails contain non ascii characters within the Subject.
Severity	Low
Tactics	InitialAccess
Techniques	T1566
Required data connectors	Corelight
Kind	Scheduled
Query frequency	1h
Query period	1h
Trigger threshold	0
Trigger operator	gt
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Corelight/Analytic Rules/CorelightSMTPEmailSubjectNonAsciiCharacters.yaml
Version	2.1.0
Arm template	50c61708-9824-46f3-87cf-22490796fae2.json

KQL

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

YAML

requiredDataConnectors:
- dataTypes:
  - Corelight_v2_smtp
  - corelight_smtp
  connectorId: Corelight
queryPeriod: 1h
triggerThreshold: 0
queryFrequency: 1h
version: 2.1.0
status: Available
severity: Low
description: |
    'Detects where an emails contain non ascii characters within the Subject.'
name: Corelight - SMTP Email containing NON Ascii Characters within the Subject
entityMappings:
- fieldMappings:
  - identifier: Recipient
    columnName: _to
  entityType: MailMessage
triggerOperator: gt
id: 50c61708-9824-46f3-87cf-22490796fae2
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Corelight/Analytic Rules/CorelightSMTPEmailSubjectNonAsciiCharacters.yaml
tactics:
- InitialAccess
relevantTechniques:
- T1566
kind: Scheduled
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

ARM