Detection: Windows Registry Dotnet ETW Disabled Via ENV Variable

Updated Date: 2025-01-07 ID: 55502381-5cce-491b-9277-7cb1d10bc0df Author: Nasreddine Bencherchali, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects a registry modification that disables the ETW for the .NET Framework. It leverages data from the Endpoint.Registry data model, specifically monitoring changes to the COMPlus_ETWEnabled registry value under the "Environment" registry key path for both user (HKCU\Environment) and machine (HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Environment) scopes. This activity is significant because disabling ETW can allow attackers to evade Endpoint Detection and Response (EDR) tools and hide their execution from audit logs. If confirmed malicious, this action could enable attackers to operate undetected, potentially leading to further compromise and persistent access within the environment.

1
2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Registry WHERE Registry.registry_path="*\\Environment*" Registry.registry_value_name="COMPlus_ETWEnabled" (Registry.registry_value_data=0x000000000 OR Registry.registry_value_data=0) BY Registry.dest Registry.user Registry.registry_path Registry.registry_key_name Registry.registry_value_name Registry.registry_value_data Registry.process_guid 
3| `drop_dm_object_name(Registry)` 
4| where isnotnull(registry_value_data) 
5| `security_content_ctime(firstTime)` 
6| `security_content_ctime(lastTime)` 
7| `windows_registry_dotnet_etw_disabled_via_env_variable_filter`

Data Source

Name Platform Sourcetype Source
Sysmon EventID 13 Windows icon Windows 'xmlwineventlog' 'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'

Macros Used

Name Value
security_content_ctime convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)
windows_registry_dotnet_etw_disabled_via_env_variable_filter search *
windows_registry_dotnet_etw_disabled_via_env_variable_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK
+ Kill Chain Phases
+ NIST
+ CIS
- Threat Actors
ID Technique Tactic
T1562.006 Indicator Blocking Defense Evasion
T1562 Impair Defenses Defense Evasion
Exploitation
DE.CM
CIS 10
APT41
APT5
Magic Hound

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting Value
Disabled true
Cron Schedule 0 * * * *
Earliest Time -70m@m
Latest Time -10m@m
Schedule Window auto
Creates Notable Yes
Rule Title %name%
Rule Description %description%
Notable Event Fields user, dest
Creates Risk Event True
This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

To successfully implement this search, you need to be ingesting logs with the registry value name, registry path, and registry value data from your endpoints. If you are using Sysmon, you must have at least version 2.0 of the official Sysmon TA. https://splunkbase.splunk.com/app/5709

Known False Positives

Setting the "COMPlus_ETWEnabled" value as a global environment variable either in user or machine scope should only happens during debugging use cases, hence the false positives rate should be very minimal.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

Modified registry entry $registry_path$ in $dest$

Risk Object Risk Object Type Risk Score Threat Objects
dest system 90 No Threat Objects
user user 90 No Threat Objects

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset XmlWinEventLog:Microsoft-Windows-Sysmon/Operational XmlWinEventLog
Integration ✅ Passing Dataset XmlWinEventLog:Microsoft-Windows-Sysmon/Operational XmlWinEventLog

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

Source: GitHub | Version: 2