Potentially Suspicious Execution From Parent Process In Public Folder

SIGMA detection rule by Florian Roth (Nextron Systems), Nasreddine Bencherchali (Nextron Systems) · GPL-2.0

Detects a potentially suspicious execution of a parent process located in the "\Users\Public" folder executing a child process containing references to shell or scripting binaries and commandlines.

title: Potentially Suspicious Execution From Parent Process In Public Folder
id: cd36cd3c-17cb-d0c6-1e77-c74a5a6e96fe
related:
    - id: 69bd9b97-2be2-41b6-9816-fb08757a4d1a
      type: derived
status: test
description: |
    Detects a potentially suspicious execution of a parent process located in the "\Users\Public" folder executing a child process containing references to shell or scripting binaries and commandlines.
references:
    - https://redcanary.com/blog/blackbyte-ransomware/
author: Florian Roth (Nextron Systems), Nasreddine Bencherchali (Nextron Systems)
date: 2022-02-25
modified: 2024-07-12
tags:
    - attack.execution
    - attack.stealth
    - attack.t1564
    - attack.t1059
logsource:
    category: process_creation
    product: windows
detection:
    process_creation:
        EventID: 4688
        Channel: Security
    selection_parent:
        ParentProcessName|contains: :\Users\Public\
    selection_child:
        - NewProcessName|endswith:
              - \bitsadmin.exe
              - \certutil.exe
              - \cmd.exe
              - \cscript.exe
              - \mshta.exe
              - \powershell.exe
              - \pwsh.exe
              - \regsvr32.exe
              - \rundll32.exe
              - \wscript.exe
        - CommandLine|contains:
              - bitsadmin
              - certutil
              - cscript
              - mshta
              - powershell
              - regsvr32
              - rundll32
              - wscript
    condition: process_creation and (all of selection_*)
falsepositives:
    - Unknown
level: high
ruletype: Sigma

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

d62a0855-5268-47d5-ad1d-cc42013cb937

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Executable code, not a declarative rule

This submission is arbitrary [[ currentRule.format ? currentRule.format.toUpperCase() : '' ]] code, not a declarative detection rule — review it as you would any script before running it, and note that it cannot be safely aggregated or auto-executed alongside YARA/Sigma/Suricata/CRS rules.

Rejected pattern present

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Format & documentation suggestions

Not a security issue — this rule is valid and was accepted as-is. These are optional fields/conventions its own format recommends, mainly affecting its quality score and how well it documents itself for other reviewers.

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[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

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