Detection rules › Sigma

Suspicious Process Parents

Status
test
Severity
high
Log source
category process_creation, product windows
Author
Florian Roth (Nextron Systems)
Source
github.com/SigmaHQ/sigma

Detects suspicious parent processes that should not have any children or should only have a single possible child program

MITRE ATT&CK coverage

TacticTechniques
Stealth

Telemetry coverage

Rule body

title: Suspicious Process Parents
id: cbec226f-63d9-4eca-9f52-dfb6652f24df
status: test
description: Detects suspicious parent processes that should not have any children or should only have a single possible child program
references:
    - https://twitter.com/x86matthew/status/1505476263464607744?s=12
    - https://svch0st.medium.com/stats-from-hunting-cobalt-strike-beacons-c17e56255f9b
author: Florian Roth (Nextron Systems)
date: 2022-03-21
modified: 2022-09-08
tags:
    - attack.stealth
    - attack.t1036
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        ParentImage|endswith:
            - '\minesweeper.exe'
            - '\winver.exe'
            - '\bitsadmin.exe'
    selection_special:
        ParentImage|endswith:
            - '\csrss.exe'
            - '\certutil.exe'
         # - '\schtasks.exe'
            - '\eventvwr.exe'
            - '\calc.exe'
            - '\notepad.exe'
    filter_special:
        Image|endswith:
            - '\WerFault.exe'
            - '\wermgr.exe'
            - '\conhost.exe' # csrss.exe, certutil.exe
            - '\mmc.exe'     # eventvwr.exe
            - '\win32calc.exe' # calc.exe
            - '\notepad.exe'
    filter_null:
        Image: null
    condition: selection or ( selection_special and not 1 of filter_* )
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: condition

selection or ( selection_special and not 1 of filter_* )

Stage 1: selection

selection:
    ParentImage|endswith:
        - '\minesweeper.exe'
        - '\winver.exe'
        - '\bitsadmin.exe'

Stage 2: selection_special

selection_special:
    ParentImage|endswith:
        - '\csrss.exe'
        - '\certutil.exe'
        - '\eventvwr.exe'
        - '\calc.exe'
        - '\notepad.exe'

Stage 3: not filter_*

filter_special:
    Image|endswith:
        - '\WerFault.exe'
        - '\wermgr.exe'
        - '\conhost.exe'
        - '\mmc.exe'
        - '\win32calc.exe'
        - '\notepad.exe'
filter_null:
    Image: null

Exclusions

The rule actively suppresses these predicates.

FieldKindExcluded valuesSearch
Imageends_with\WerFault.exeexcludes:Image field:"Image" value:"\WerFault.exe"
Imageends_with\conhost.exeexcludes:Image field:"Image" value:"\conhost.exe"
Imageends_with\mmc.exeexcludes:Image field:"Image" value:"\mmc.exe"
Imageends_with\notepad.exeexcludes:Image field:"Image" value:"\notepad.exe"
Imageends_with\wermgr.exeexcludes:Image field:"Image" value:"\wermgr.exe"
Imageends_with\win32calc.exeexcludes:Image field:"Image" value:"\win32calc.exe"
Imageis_null(no value, null check)excludes:Image

Indicators

These rows show field, operator, and value matches.

FieldKindValuesSearch
ParentImageends_with
  • \bitsadmin.exe
  • \calc.exe
  • \certutil.exe
  • \csrss.exe corpus 3 (sigma 3)
  • \eventvwr.exe corpus 2 (sigma 2)
  • \minesweeper.exe
  • \notepad.exe
  • \winver.exe
field:"ParentImage" kind:ends_with