Detection: Windows Schtasks Create Run As System

Updated Date: 2024-08-15 ID: 41a0e58e-884c-11ec-9976-acde48001122 Author: Michael Haag, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects the creation of a new scheduled task using Schtasks.exe to run as the SYSTEM user. This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on command-line executions and process details. This activity is significant as it often indicates an attempt to gain elevated privileges or maintain persistence within the environment. If confirmed malicious, an attacker could execute code with SYSTEM-level privileges, potentially leading to data theft, ransomware deployment, or further system compromise. Immediate investigation and mitigation are crucial to prevent further damage.

Search

1
2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where `process_schtasks` Processes.process="*/create *" AND Processes.process="*/ru *" AND Processes.process="*system*" by Processes.dest Processes.user Processes.parent_process_name Processes.process_name Processes.original_file_name Processes.process Processes.process_id Processes.parent_process_id 
3| `drop_dm_object_name(Processes)` 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `windows_schtasks_create_run_as_system_filter`

Data Source

Name	Platform	Sourcetype	Source	Supported App
CrowdStrike ProcessRollup2	N/A	`'crowdstrike:events:sensor'`	`'crowdstrike'`	N/A

Macros Used

Name	Value
process_schtasks	`(Processes.process_name=schtasks.exe OR Processes.original_file_name=schtasks.exe)`
windows_schtasks_create_run_as_system_filter	`search *`

windows_schtasks_create_run_as_system_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
T1053.005	Scheduled Task	Execution
T1053	Scheduled Task/Job	Persistence

KillChainPhase.EXPLOITAITON

KillChainPhase.INSTALLATION

NistCategory.DE_CM

Cis18Value.CIS_10

APT-C-36

APT29

APT3

APT32

APT33

APT37

APT38

APT39

APT41

BITTER

BRONZE BUTLER

Blue Mockingbird

Chimera

Cobalt Group

Confucius

Dragonfly

FIN10

FIN13

FIN6

FIN7

FIN8

Fox Kitten

GALLIUM

Gamaredon Group

HEXANE

Higaisa

Kimsuky

Lazarus Group

LuminousMoth

Machete

Magic Hound

Molerats

MuddyWater

Mustang Panda

Naikon

OilRig

Patchwork

Rancor

Silence

Stealth Falcon

TA2541

ToddyCat

Wizard Spider

menuPass

Earth Lusca

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

The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the Processes node of the Endpoint data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.

Known False Positives

False positives will be limited to legitimate applications creating a task to run as SYSTEM. Filter as needed based on parent process, or modify the query to have world writeable paths to restrict it.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
An $process_name$ was created on endpoint $dest$ attempting to spawn as SYSTEM.	48	80	60

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: 3