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Detection rules › Sigma

Potentially Suspicious Child Process of KeyScrambler.exe

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

Detects potentially suspicious child processes of KeyScrambler.exe

MITRE ATT&CK coverage

TacticTechniques
ExecutionT1203 Exploitation for Client Execution, T1574.001 Hijack Execution Flow: DLL
StealthT1574.001 Hijack Execution Flow: DLL

Event coverage

ProviderEventTitle
SysmonEvent ID 1Process creation

Rule body yaml

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

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
Imageends_with
  • \cmd.exe corpus 130 (sigma 130)
  • \cscript.exe corpus 73 (sigma 73)
  • \mshta.exe corpus 67 (sigma 67)
  • \powershell.exe corpus 182 (sigma 182)
  • \pwsh.exe corpus 168 (sigma 168)
  • \regsvr32.exe corpus 65 (sigma 65)
  • \rundll32.exe corpus 95 (sigma 95)
  • \wscript.exe corpus 75 (sigma 75)
OriginalFileNameeq
  • Cmd.Exe corpus 65 (sigma 43, splunk 17, elastic 5)
  • PowerShell.EXE corpus 120 (sigma 84, splunk 30, elastic 6)
  • RUNDLL32.EXE corpus 62 (sigma 35, splunk 21, elastic 6)
  • cscript.exe corpus 19 (sigma 17, elastic 2)
  • mshta.exe corpus 22 (sigma 13, splunk 6, elastic 3)
  • pwsh.dll corpus 112 (sigma 79, splunk 30, elastic 3)
  • regsvr32.exe corpus 26 (sigma 17, splunk 6, elastic 3)
  • wscript.exe corpus 20 (sigma 17, elastic 3)
ParentImageends_with
  • \KeyScrambler.exe