prsstn-wmi-sbscrp

name	prsstn-wmi-sbscrp
description	Hunt for adversary persistence through Windows Management Instrumentation event subscriptions by monitoring WMI consumer, filter, and binding creation events that execute malicious code triggered by system events.
domain	cybersecurity
subdomain	threat-hunting
tags	["threat-hunting","wmi-persistence","mitre-t1546-003","event-subscription","windows","endpoint-detection"]
version	1.0
author	mahipal
license	Apache-2.0
d3fend_techniques	["Application Protocol Command Analysis","Network Isolation","Network Traffic Analysis","Client-server Payload Profiling","Platform Monitoring"]
nist_csf	["DE.CM-01","DE.AE-02","DE.AE-07","ID.RA-05"]

Hunting for Persistence via WMI Subscriptions

When to Use

• When proactively searching for fileless persistence mechanisms in Windows environments
• After threat intelligence reports indicate WMI-based persistence by APT groups (APT29, APT32, FIN8)
• When investigating systems where malware persists across reboots despite cleanup attempts
• During incident response when standard persistence locations (Run keys, scheduled tasks) are clean
• When WmiPrvSe.exe is observed spawning unexpected child processes

Prerequisites

• Sysmon Event ID 19, 20, 21 (WMI Event Filter/Consumer/Binding) enabled
• Windows Event ID 5861 (WMI activity logging) from Microsoft-Windows-WMI-Activity
• PowerShell logging enabled (Script Block Logging, Module Logging)
• WMI repository access for enumeration
• SIEM platform for event correlation

Workflow

1. Enumerate Existing WMI Subscriptions: Query all permanent WMI event subscriptions on target systems. A clean system typically has very few or zero permanent subscriptions, making anomalies easy to spot.
2. Monitor WMI Event Creation (Sysmon 19/20/21): Sysmon Event 19 captures WmiEventFilter activity, Event 20 captures WmiEventConsumer activity, and Event 21 captures WmiEventConsumerToFilter binding.
3. Analyze Consumer Types: Focus on ActiveScriptEventConsumer (runs VBScript/JScript) and CommandLineEventConsumer (executes commands) -- these are the dangerous types used for persistence.
4. Check Event Filter Triggers: Examine what triggers the subscription. Common malicious triggers include system startup (Win32_ProcessStartTrace), user logon, or timer-based execution intervals.
5. Investigate WmiPrvSe.exe Child Processes: When a WMI subscription fires, the action is executed by WmiPrvSe.exe. Hunt for unusual child processes of WmiPrvSe.exe.
6. Correlate with MOF Compilation: Detect mofcomp.exe usage which compiles MOF files to create WMI subscriptions programmatically.
7. Validate and Respond: Confirm malicious subscriptions, remove them, and trace back to the initial infection vector.

Key Concepts

Concept	Description
T1546.003	Event Triggered Execution: WMI Event Subscription
__EventFilter	WMI class defining the trigger condition