Cisco SEG - Unexpected attachment

Back


Id	f8ba18c4-81e3-4db0-8f85-4989f2ed2ade
Rulename	Cisco SEG - Unexpected attachment
Description	Detects possibly malicious attachments.
Severity	High
Tactics	InitialAccess
Techniques	T1566
Required data connectors	CefAma
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/CiscoSEG/Analytic Rules/CiscoSEGUnexpextedAttachment.yaml
Version	1.0.3
Arm template	f8ba18c4-81e3-4db0-8f85-4989f2ed2ade.json

KQL

CiscoSEGEvent
| where NetworkDirection =~ 'Incoming'
| where tostring(AdditionalFields) has 'ESAAttachmentDetails'
| extend attachment = replace_string(tostring(extract(@'"ESAAttachmentDetails":"{(.*?):', 1, tostring(AdditionalFields))), "'", "")
| where attachment endswith '.ps1' or attachment endswith '.lnk' or attachment endswith '.exe'
| extend AccountCustomEntity = DstUserName

YAML

name: Cisco SEG - Unexpected attachment
queryFrequency: 1h
description: |
    'Detects possibly malicious attachments.'
relevantTechniques:
- T1566
id: f8ba18c4-81e3-4db0-8f85-4989f2ed2ade
triggerOperator: gt
version: 1.0.3
entityMappings:
- entityType: Account
  fieldMappings:
  - columnName: AccountCustomEntity
    identifier: Name
kind: Scheduled
status: Available
tactics:
- InitialAccess
triggerThreshold: 0
queryPeriod: 1h
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/CiscoSEG/Analytic Rules/CiscoSEGUnexpextedAttachment.yaml
requiredDataConnectors:
- dataTypes:
  - CommonSecurityLog
  connectorId: CefAma
query: |
  CiscoSEGEvent
  | where NetworkDirection =~ 'Incoming'
  | where tostring(AdditionalFields) has 'ESAAttachmentDetails'
  | extend attachment = replace_string(tostring(extract(@'"ESAAttachmentDetails":"{(.*?):', 1, tostring(AdditionalFields))), "'", "")
  | where attachment endswith '.ps1' or attachment endswith '.lnk' or attachment endswith '.exe'
  | extend AccountCustomEntity = DstUserName  
severity: High

ARM