Windows Process Creation: .NET ETW Logging Environment Variables Set via Command Line

Flags process command lines setting COMPlus_ETWEnabled/COMPlus_ETWFlags, potentially impairing ETW logging for .NET.

FreeUnreviewedSigmahighv1

windows-process-creation-net-etw-logging-environment-variables-set-via-command-l-41421f44

title: "Windows Process Creation: .NET ETW Logging Environment Variables Set via Command Line"
id: 92dd0e4a-7590-4517-b8bc-011bd998c054
status: test
description: This rule matches Windows process creation events whose command line contains the .NET runtime environment configuration variables COMPlus_ETWEnabled and COMPlus_ETWFlags. An attacker may use these runtime configuration knobs to influence ETW logging behavior in .NET processes as part of defense evasion. The detection relies on process creation telemetry with command-line content.
references:
  - https://twitter.com/_xpn_/status/1268712093928378368
  - https://social.msdn.microsoft.com/Forums/vstudio/en-US/0878832e-39d7-4eaf-8e16-a729c4c40975/what-can-i-use-e13c0d23ccbc4e12931bd9cc2eee27e4-for?forum=clr
  - https://github.com/dotnet/runtime/blob/ee2355c801d892f2894b0f7b14a20e6cc50e0e54/docs/design/coreclr/jit/viewing-jit-dumps.md#setting-configuration-variables
  - https://github.com/dotnet/runtime/blob/f62e93416a1799aecc6b0947adad55a0d9870732/src/coreclr/src/inc/clrconfigvalues.h#L35-L38
  - https://github.com/dotnet/runtime/blob/7abe42dc1123722ed385218268bb9fe04556e3d3/src/coreclr/src/inc/clrconfig.h#L33-L39
  - https://github.com/dotnet/runtime/search?p=1&q=COMPlus_&unscoped_q=COMPlus_
  - https://bunnyinside.com/?term=f71e8cb9c76a
  - http://managed670.rssing.com/chan-5590147/all_p1.html
  - https://github.com/dotnet/runtime/blob/4f9ae42d861fcb4be2fcd5d3d55d5f227d30e723/docs/coding-guidelines/clr-jit-coding-conventions.md#1412-disabling-code
  - https://i.blackhat.com/EU-21/Wednesday/EU-21-Teodorescu-Veni-No-Vidi-No-Vici-Attacks-On-ETW-Blind-EDRs.pdf
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_susp_etw_modification_cmdline.yml
author: Roberto Rodriguez (Cyb3rWard0g), OTR (Open Threat Research), Huntrule Team
date: 2020-05-02
modified: 2022-12-09
tags:
  - attack.defense-impairment
  - attack.t1685
logsource:
  category: process_creation
  product: windows
detection:
  selection:
    CommandLine|contains:
      - COMPlus_ETWEnabled
      - COMPlus_ETWFlags
  condition: selection
falsepositives:
  - Unlikely
level: high
license: DRL-1.1
related:
  - id: 41421f44-58f9-455d-838a-c398859841d4
    type: derived

What it detects

This rule matches Windows process creation events whose command line contains the .NET runtime environment configuration variables COMPlus_ETWEnabled and COMPlus_ETWFlags. An attacker may use these runtime configuration knobs to influence ETW logging behavior in .NET processes as part of defense evasion. The detection relies on process creation telemetry with command-line content.

Known false positives

Unlikely

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.