Detection: Schedule Task with Rundll32 Command Trigger

Updated Date: 2024-05-15 ID: 75b00fd8-a0ff-11eb-8b31-acde48001122 Author: Teoderick Contreras, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects the creation of scheduled tasks in Windows that use the rundll32 command. It leverages Windows Security EventCode 4698, which logs the creation of scheduled tasks, and filters for tasks executed via rundll32. This activity is significant as it is a common technique used by malware, such as TrickBot, to persist in an environment or deliver additional payloads. If confirmed malicious, this could lead to data theft, ransomware deployment, or other damaging outcomes. Immediate investigation and mitigation are crucial to prevent further compromise.

Search

1`wineventlog_security` EventCode=4698 
2| xmlkv Message 
3| search Command IN ("*rundll32*") 
4| stats count min(_time) as firstTime max(_time) as lastTime by dest, Task_Name, Command, Author, Enabled, Hidden, Arguments 
5| `security_content_ctime(firstTime)` 
6| `security_content_ctime(lastTime)` 
7| `schedule_task_with_rundll32_command_trigger_filter`

Data Source

Name	Platform	Sourcetype	Source	Supported App
Windows Event Log Security 4698	Windows	`'xmlwineventlog'`	`'XmlWinEventLog:Security'`	N/A

Macros Used

Name	Value
security_content_ctime	`convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)`
schedule_task_with_rundll32_command_trigger_filter	`search *`

schedule_task_with_rundll32_command_trigger_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	Scheduled Task/Job	Execution

KillChainPhase.EXPLOITAITON

KillChainPhase.INSTALLATION

NistCategory.DE_CM

Cis18Value.CIS_10

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

To successfully implement this search, you need to be ingesting logs with the task schedule (Exa. Security Log EventCode 4698) endpoints. Tune and filter known instances of Task schedule used in your environment.

Known False Positives

unknown

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
A schedule task process commandline rundll32 arguments $Arguments$ in host $dest$	70	70	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	`WinEventLog:Security`	`WinEventLog`
Integration	✅ Passing	Dataset	`WinEventLog:Security`	`WinEventLog`

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