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Description

The following analytic detects the creation of suspicious tasks in Windows, specifically tasks using the rundll32 command. It's implemented using Windows Security EventCode 4698 for A scheduled task was created, and looks for tasks executed either via schtasks.exe or TaskService. This behavior is worth identifying as it is commonly used by malware, such as TrickBot, that leverages rundll32 to execute its downloader.
If a true positive is found, it suggests an attacker is trying to persist within the environment or potentially deliver additional malicious payloads, leading to data theft, ransomware, or other damaging outcomes.
To implement this analytic, ensure you are ingesting logs with task schedule information from your endpoints. Be aware of potential false positives - legitimate uses of Task Scheduler in your environment may cause benign activities to be flagged.
Upon triage, review the scheduled task's source and the command to be executed. Capture and inspect any relevant on-disk artifacts, and look for concurrent processes to identify the attack source. This approach helps analysts detect potential threats earlier and mitigate the risks.

  • Type: TTP

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2021-04-19
  • Author: Teoderick Contreras, Splunk
  • ID: 75b00fd8-a0ff-11eb-8b31-acde48001122

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1053 Scheduled Task/Job Execution, Persistence, Privilege Escalation
Kill Chain Phase
  • Installation
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


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

Macros

The SPL above uses the following Macros:

:information_source: schedule_task_with_rundll32_command_trigger_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • dest
  • Task_Name
  • Command
  • Author
  • Enabled
  • Hidden
  • Arguments

How To Implement

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

RBA

Risk Score Impact Confidence Message
70.0 70 100 A schedule task process commandline rundll32 arguments $Arguments$ in host $dest$

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

Reference

Test Dataset

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 | version: 1