Windows Sysmon Driver Altitude Registry Changes

Identifies registry writes that change the Sysmon instance altitude value, which can disrupt Sysmon loading at boot.

FreeUnreviewedSigmahighv1

windows-sysmon-driver-altitude-registry-changes-4916a35e

title: Windows Sysmon Driver Altitude Registry Changes
id: b4b4d16c-4d2d-40ed-a6aa-f8e7ba1e0be0
status: test
description: This rule matches registry writes that update the Sysmon instance altitude value under the Services Instances path. Changing the driver altitude can be used to interfere with Sysmon’s ability to load correctly at boot, impacting monitoring through defense impairment. Detection relies on registry set events containing the TargetObject paths that include \Services\ and end with \Instances\Sysmon Instance\Altitude.
references:
  - https://posts.specterops.io/shhmon-silencing-sysmon-via-driver-unload-682b5be57650
  - https://youtu.be/zSihR3lTf7g
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/registry/registry_set/registry_set_change_sysmon_driver_altitude.yml
author: B.Talebi, Huntrule Team
date: 2022-07-28
modified: 2024-03-25
tags:
  - attack.defense-impairment
  - attack.t1685
logsource:
  category: registry_set
  product: windows
detection:
  selection:
    TargetObject|contains: \Services\
    TargetObject|endswith: \Instances\Sysmon Instance\Altitude
  condition: selection
falsepositives:
  - Legitimate driver altitude change to hide sysmon
level: high
license: DRL-1.1
related:
  - id: 4916a35e-bfc4-47d0-8e25-a003d7067061
    type: derived

What it detects

This rule matches registry writes that update the Sysmon instance altitude value under the Services Instances path. Changing the driver altitude can be used to interfere with Sysmon’s ability to load correctly at boot, impacting monitoring through defense impairment. Detection relies on registry set events containing the TargetObject paths that include \Services\ and end with \Instances\Sysmon Instance\Altitude.

Known false positives

Legitimate driver altitude change to hide sysmon

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