SlackAudit - Suspicious file downloaded

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Id	132b98a5-07e9-401a-9b6f-453e52a53979
Rulename	SlackAudit - Suspicious file downloaded.
Description	Detects potentialy suspicious downloads.
Severity	Medium
Tactics	InitialAccess
Techniques	T1189
Required data connectors	SlackAuditAPI
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/SlackAudit/Analytic Rules/SlackAuditSuspiciousFileDownloaded.yaml
Version	1.0.1
Arm template	132b98a5-07e9-401a-9b6f-453e52a53979.json

KQL

SlackAudit
| where DvcAction =~ 'file_downloaded'
| extend FileName = tostring(EntityFileName)
| extend fe = split(FileName, '.')
| extend FileExtension = iff(array_length(fe) > 1, tostring(fe[-1]), '')
| where FileName contains '.'
| where FileExtension matches regex @"^[A-Za-z]{1,4}$"
| project EntityFileName = FileName, SrcUserName
| extend AccountCustomEntity = SrcUserName
| extend FileCustomEntity = EntityFileName

YAML

entityMappings:
- entityType: Account
  fieldMappings:
  - identifier: FullName
    columnName: AccountCustomEntity
- entityType: File
  fieldMappings:
  - identifier: Name
    columnName: FileCustomEntity
tactics:
- InitialAccess
requiredDataConnectors:
- dataTypes:
  - SlackAudit_CL
  connectorId: SlackAuditAPI
alertDetailsOverride:
  alertDisplayNameFormat: 'Suspicious Slack file downloaded by {{SrcUserName}}: {{EntityFileName}}'
  alertDescriptionFormat: A Slack audit file_downloaded event matched the suspicious extension heuristic for {{EntityFileName}} by {{SrcUserName}}.
id: 132b98a5-07e9-401a-9b6f-453e52a53979
severity: Medium
status: Available
customDetails:
  UserName: SrcUserName
  FileName: EntityFileName
query: |
  SlackAudit
  | where DvcAction =~ 'file_downloaded'
  | extend FileName = tostring(EntityFileName)
  | extend fe = split(FileName, '.')
  | extend FileExtension = iff(array_length(fe) > 1, tostring(fe[-1]), '')
  | where FileName contains '.'
  | where FileExtension matches regex @"^[A-Za-z]{1,4}$"
  | project EntityFileName = FileName, SrcUserName
  | extend AccountCustomEntity = SrcUserName
  | extend FileCustomEntity = EntityFileName  
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/SlackAudit/Analytic Rules/SlackAuditSuspiciousFileDownloaded.yaml
kind: Scheduled
queryPeriod: 1h
version: 1.0.1
name: SlackAudit - Suspicious file downloaded.
queryFrequency: 1h
triggerThreshold: 0
relevantTechniques:
- T1189
description: |
    'Detects potentialy suspicious downloads.'
triggerOperator: gt

ARM