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Detection rules › Sigma

Suspicious Processes Spawned by WinRM

Status
test
Severity
high
Log source
category process_creation, product windows
Author
Andreas Hunkeler (@Karneades), Markus Neis
Source
github.com/SigmaHQ/sigma

Detects suspicious processes including shells spawnd from WinRM host process

Known false positives

  • Legitimate WinRM usage

MITRE ATT&CK coverage

TacticTechniques
Initial Access

Telemetry coverage

ProviderRecord / event type
SysmonEvent ID 1: Process creation
Security-AuditingEvent ID 4688: A new process has been created.

Rule body

title: Suspicious Processes Spawned by WinRM
id: 5cc2cda8-f261-4d88-a2de-e9e193c86716
status: test
description: Detects suspicious processes including shells spawnd from WinRM host process
author: Andreas Hunkeler (@Karneades), Markus Neis
references:
    - Internal Research
date: 2021-05-20
modified: 2022-07-14
tags:
    - attack.t1190
    - attack.initial-access
    - attack.persistence
    - attack.privilege-escalation
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        ParentImage|endswith: '\wsmprovhost.exe'
        Image|endswith:
            - '\cmd.exe'
            - '\sh.exe'
            - '\bash.exe'
            - '\powershell.exe'
            - '\pwsh.exe'
            - '\wsl.exe'
            - '\schtasks.exe'
            - '\certutil.exe'
            - '\whoami.exe'
            - '\bitsadmin.exe'
    condition: selection
falsepositives:
    - Legitimate WinRM usage
level: high

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    ParentImage|endswith: '\wsmprovhost.exe'
    Image|endswith:
        - '\cmd.exe'
        - '\sh.exe'
        - '\bash.exe'
        - '\powershell.exe'
        - '\pwsh.exe'
        - '\wsl.exe'
        - '\schtasks.exe'
        - '\certutil.exe'
        - '\whoami.exe'
        - '\bitsadmin.exe'

Indicators

These rows show field, operator, and value matches.

FieldKindValuesSearch
Imageends_with
  • \bash.exe corpus 21 (sigma 21)
  • \bitsadmin.exe corpus 29 (sigma 29)
  • \certutil.exe corpus 44 (sigma 43, kusto 1)
  • \cmd.exe corpus 130 (sigma 130)
  • \powershell.exe corpus 179 (sigma 178, kusto 1)
  • \pwsh.exe corpus 165 (sigma 164, kusto 1)
  • \schtasks.exe corpus 55 (sigma 55)
  • \sh.exe corpus 16 (sigma 16)
  • \whoami.exe corpus 19 (sigma 19)
  • \wsl.exe corpus 11 (sigma 11)
field:"Image" kind:ends_with
ParentImageends_with
  • \wsmprovhost.exe corpus 2 (sigma 2)
field:"ParentImage" kind:ends_with value:"\wsmprovhost.exe"