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

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

ARM