Detection: WMI Permanent Event Subscription - Sysmon

Updated Date: 2024-09-30 ID: ad05aae6-3b2a-4f73-af97-57bd26cee3b9 Author: Rico Valdez, Michael Haag, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic identifies the creation of WMI permanent event subscriptions, which can be used to establish persistence or perform privilege escalation. It leverages Sysmon data, specifically EventCodes 19, 20, and 21, to detect the creation of WMI EventFilters, EventConsumers, and FilterToConsumerBindings. This activity is significant as it may indicate an attacker setting up mechanisms to execute code with elevated SYSTEM privileges when specific events occur. If confirmed malicious, this could allow the attacker to maintain persistence, escalate privileges, and execute arbitrary code, posing a severe threat to the environment.

1`sysmon` EventCode=21 
2| rename host as dest 
3| table _time, dest, user, Operation, EventType, Query, Consumer, Filter 
4| `wmi_permanent_event_subscription___sysmon_filter`

Data Source

Name Platform Sourcetype Source
Sysmon EventID 21 Windows icon Windows 'xmlwineventlog' 'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'

Macros Used

Name Value
sysmon sourcetype=XmlWinEventLog:Microsoft-Windows-Sysmon/Operational OR source=XmlWinEventLog:Microsoft-Windows-Sysmon/Operational OR source=Syslog:Linux-Sysmon/Operational
wmi_permanent_event_subscription___sysmon_filter search *
wmi_permanent_event_subscription___sysmon_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 must be collecting Sysmon data using Sysmon version 6.1 or greater and have Sysmon configured to generate alerts for WMI activity (eventID= 19, 20, 21). In addition, you must have at least version 6.0.4 of the Sysmon TA installed to properly parse the fields.

Known False Positives

Although unlikely, administrators may use event subscriptions for legitimate purposes.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
WMI Permanent Event Subscription detected on $dest$ by $user$ 30 30 100
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: 4