Headless Process Launched Via Conhost.EXE

Status: test
Severity: medium
Log source: category process_creation, product windows
Author: Nasreddine Bencherchali (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects the launch of a child process via "conhost.exe" with the "--headless" flag. The "--headless" flag hides the windows from the user upon execution.

MITRE ATT&CK coverage

Tactic	Techniques
Execution	`T1059.001` Command and Scripting Interpreter: PowerShell `T1059.003` Command and Scripting Interpreter: Windows Command Shell

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation

Rule body

title: Headless Process Launched Via Conhost.EXE
id: 00ca75ab-d5ce-43be-b86c-55ff39c6abfc
related:
    - id: 056c7317-9a09-4bd4-9067-d051312752ea
      type: derived
status: test
description: |
    Detects the launch of a child process via "conhost.exe" with the "--headless" flag.
    The "--headless" flag hides the windows from the user upon execution.
references:
    - https://www.huntress.com/blog/fake-browser-updates-lead-to-boinc-volunteer-computing-software
author: Nasreddine Bencherchali (Nextron Systems)
date: 2024-07-23
tags:
    - attack.execution
    - attack.t1059.001
    - attack.t1059.003
    - detection.threat-hunting
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        ParentImage|endswith: '\conhost.exe'
        ParentCommandLine|contains: '--headless'
    condition: selection
falsepositives:
    - Unknown
level: medium

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    ParentImage|endswith: '\conhost.exe'
    ParentCommandLine|contains: '--headless'

Indicators

These rows show field, operator, and value matches.

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