Uncommon Child Process Of Conhost.EXE

Status: test
Severity: medium
Log source: category process_creation, product windows
Author: omkar72
Source: github.com/SigmaHQ/sigma

Detects uncommon "conhost" child processes. This could be a sign of "conhost" usage as a LOLBIN or potential process injection activity.

MITRE ATT&CK coverage

Tactic	Techniques
Stealth	`T1202` Indirect Command Execution

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation
Security-Auditing	Event ID 4688: A new process has been created.

Rule body

title: Uncommon Child Process Of Conhost.EXE
id: 7dc2dedd-7603-461a-bc13-15803d132355
related:
    - id: dfa03a09-8b92-4d83-8e74-f72839b1c407
      type: similar
status: test
description: Detects uncommon "conhost" child processes. This could be a sign of "conhost" usage as a LOLBIN or potential process injection activity.
references:
    - http://www.hexacorn.com/blog/2020/05/25/how-to-con-your-host/
author: omkar72
date: 2020-10-25
modified: 2023-12-11
tags:
    - attack.stealth
    - attack.t1202
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        ParentImage|endswith: '\conhost.exe'
    filter_main_conhost:
        Image|endswith: ':\Windows\System32\conhost.exe'
    filter_main_null:
        Image: null
    filter_main_empty:
        Image: ''
    filter_optional_provider:
        Provider_Name: 'SystemTraceProvider-Process'  # Race condition with SystemTrace doesn't provide all fields.
    condition: selection and not 1 of filter_main_* and not 1 of filter_optional_*
falsepositives:
    - Unknown
level: medium

Stages and Predicates

Stage 0: `condition`

selection and not 1 of filter_main_* and not 1 of filter_optional_*

Stage 1: `selection`

selection:
    ParentImage|endswith: '\conhost.exe'

Stage 2: `not filter_main_*`

filter_main_conhost:
    Image|endswith: ':\Windows\System32\conhost.exe'
filter_main_null:
    Image: null
filter_main_empty:
    Image: ''

Stage 3: `not filter_optional_provider`

filter_optional_provider:
    Provider_Name: 'SystemTraceProvider-Process'

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`Image`	ends_with	`:\Windows\System32\conhost.exe`	`excludes:Image` `field:"Image" value:":\Windows\System32\conhost.exe"`
`Image`	is_null	(no value, null check)	`excludes:Image`
`Provider_Name`	eq	`SystemTraceProvider-Process`	`excludes:Provider_Name` `field:"Provider_Name" value:"SystemTraceProvider-Process"`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`ParentImage`	ends_with	`\conhost.exe` corpus 4 (sigma 4)	`field:"ParentImage" kind:ends_with value:"\conhost.exe"`