Privilege Escalation via Windir Environment Variable

Identifies a privilege escalation attempt via a rogue Windows directory (Windir) environment variable. This is a known primitive that is often combined with other vulnerabilities to elevate privileges.

Rule type: eql

Rule indices:

logs-endpoint.events.registry-*
endgame-*
logs-windows.sysmon_operational-*

Severity: high

Risk score: 73

Runs every: 5m

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

https://www.tiraniddo.dev/2017/05/exploiting-environment-variables-in.html

Tags:

Domain: Endpoint
OS: Windows
Use Case: Threat Detection
Tactic: Privilege Escalation
Data Source: Elastic Endgame
Data Source: Elastic Defend
Data Source: Sysmon

Version: 107

Rule authors:

Elastic

Rule license: Elastic License v2

Rule query

edit

registry where host.os.type == "windows" and event.type == "change" and
registry.value : ("windir", "systemroot") and
registry.path : (
    "HKEY_USERS\\*\\Environment\\windir",
    "HKEY_USERS\\*\\Environment\\systemroot",
    "HKU\\*\\Environment\\windir",
    "HKU\\*\\Environment\\systemroot",
    "\\REGISTRY\\USER\\*\\Environment\\windir",
    "\\REGISTRY\\USER\\*\\Environment\\systemroot"
    ) and
 not registry.data.strings : ("C:\\windows", "%SystemRoot%")

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Privilege Escalation
- ID: TA0004
- Reference URL: https://attack.mitre.org/tactics/TA0004/
Technique:
- Name: Hijack Execution Flow
- ID: T1574
- Reference URL: https://attack.mitre.org/techniques/T1574/
Sub-technique:
- Name: Path Interception by PATH Environment Variable
- ID: T1574.007
- Reference URL: https://attack.mitre.org/techniques/T1574/007/

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