Detection: Detect WMI Event Subscription Persistence

Updated Date: 2024-05-15 ID: 01d9a0c2-cece-11eb-ab46-acde48001122 Author: Michael Haag, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic identifies the creation of WMI Event Subscriptions, which can be used to establish persistence or perform privilege escalation. It detects EventID 19 (EventFilter creation), EventID 20 (EventConsumer creation), and EventID 21 (FilterToConsumerBinding creation) from Sysmon logs. This activity is significant because WMI Event Subscriptions can execute code with elevated SYSTEM privileges, making it a powerful persistence mechanism. If confirmed malicious, an attacker could maintain long-term access, escalate privileges, and execute arbitrary code, posing a severe threat to the environment.

Search

1`sysmon` EventID=20 
2| stats count min(_time) as firstTime max(_time) as lastTime by Computer User Destination 
3| rename Computer as dest 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `detect_wmi_event_subscription_persistence_filter`

Data Source

Name	Platform	Sourcetype	Source	Supported App
Sysmon EventID 20	Windows	`'xmlwineventlog'`	`'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'`	N/A

Macros Used

Name	Value
security_content_ctime	`convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)`
detect_wmi_event_subscription_persistence_filter	`search *`

detect_wmi_event_subscription_persistence_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
T1546.003	Windows Management Instrumentation Event Subscription	Persistence
T1546	Event Triggered Execution	Privilege Escalation

KillChainPhase.EXPLOITAITON

KillChainPhase.INSTALLATION

NistCategory.DE_CM

Cis18Value.CIS_10

APT29

APT33

Blue Mockingbird

FIN8

HEXANE

Leviathan

Metador

Mustang Panda

Rancor

Turla

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 that provide WMI Event Subscription from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA and have enabled EventID 19, 20 and 21. Tune and filter known good to limit the volume.

Known False Positives

It is possible some applications will create a consumer and may be required to be filtered. For tuning, add any additional LOLBin's for further depth of coverage.

Associated Analytic Story

Suspicious WMI Use

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
Possible malicious WMI Subscription created on $dest$	63	70	90

The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

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