Detection rules › Sigma

Potentially Suspicious Child Process of KeyScrambler.exe

Status
test
Severity
medium
Log source
category process_creation, product windows
Author
Swachchhanda Shrawan Poudel
Source
github.com/SigmaHQ/sigma

Detects potentially suspicious child processes of KeyScrambler.exe

MITRE ATT&CK coverage

Telemetry coverage

ProviderRecord / event type
SysmonEvent ID 1: Process creation

Rule body

title: Potentially Suspicious Child Process of KeyScrambler.exe
id: ca5583e9-8f80-46ac-ab91-7f314d13b984
related:
    - id: d2451be2-b582-4e15-8701-4196ac180260
      type: similar
status: test
description: Detects potentially suspicious child processes of KeyScrambler.exe
references:
    - https://twitter.com/DTCERT/status/1712785421845790799
author: Swachchhanda Shrawan Poudel
date: 2024-05-13
tags:
    - attack.persistence
    - attack.execution
    - attack.privilege-escalation
    - attack.stealth
    - attack.t1203
    - attack.t1574.001
logsource:
    category: process_creation
    product: windows
detection:
    selection_parent:
        ParentImage|endswith: '\KeyScrambler.exe'
    selection_binaries:
        # Note: add additional binaries that the attacker might use
        - Image|endswith:
              - '\cmd.exe'
              - '\cscript.exe'
              - '\mshta.exe'
              - '\powershell.exe'
              - '\pwsh.exe'
              - '\regsvr32.exe'
              - '\rundll32.exe'
              - '\wscript.exe'
        - OriginalFileName:
              - 'Cmd.Exe'
              - 'cscript.exe'
              - 'mshta.exe'
              - 'PowerShell.EXE'
              - 'pwsh.dll'
              - 'regsvr32.exe'
              - 'RUNDLL32.EXE'
              - 'wscript.exe'
    condition: all of selection_*
falsepositives:
    - Unknown
level: medium

Stages and Predicates

Stage 0: condition

all of selection_*

Stage 1: selection_parent

selection_parent:
    ParentImage|endswith: '\KeyScrambler.exe'

Stage 2: selection_binaries

selection_binaries:
    - Image|endswith:
          - '\cmd.exe'
          - '\cscript.exe'
          - '\mshta.exe'
          - '\powershell.exe'
          - '\pwsh.exe'
          - '\regsvr32.exe'
          - '\rundll32.exe'
          - '\wscript.exe'
    - OriginalFileName:
          - 'Cmd.Exe'
          - 'cscript.exe'
          - 'mshta.exe'
          - 'PowerShell.EXE'
          - 'pwsh.dll'
          - 'regsvr32.exe'
          - 'RUNDLL32.EXE'
          - 'wscript.exe'

Indicators

These rows show field, operator, and value matches.

FieldKindValuesSearch
Imageends_with
  • \cmd.exe corpus 130 (sigma 130)
  • \cscript.exe corpus 72 (sigma 72)
  • \mshta.exe corpus 66 (sigma 66)
  • \powershell.exe corpus 179 (sigma 178, kusto 1)
  • \pwsh.exe corpus 165 (sigma 164, kusto 1)
  • \regsvr32.exe corpus 64 (sigma 64)
  • \rundll32.exe corpus 94 (sigma 94)
  • \wscript.exe corpus 74 (sigma 74)
field:"Image" kind:ends_with
OriginalFileNameeq
  • Cmd.Exe corpus 81 (sigma 43, elastic 21, splunk 17)
  • PowerShell.EXE corpus 138 (sigma 84, splunk 30, elastic 24)
  • RUNDLL32.EXE corpus 78 (sigma 35, elastic 22, splunk 21)
  • cscript.exe corpus 32 (sigma 17, elastic 15)
  • mshta.exe corpus 40 (elastic 21, sigma 13, splunk 6)
  • pwsh.dll corpus 112 (sigma 79, splunk 30, elastic 3)
  • regsvr32.exe corpus 37 (sigma 17, elastic 15, splunk 5)
  • wscript.exe corpus 38 (elastic 21, sigma 17)
field:"OriginalFileName" kind:eq
ParentImageends_with
  • \KeyScrambler.exe
field:"ParentImage" kind:ends_with value:"\KeyScrambler.exe"