:warning: THIS IS A EXPERIMENTAL DETECTION

This detection has been marked experimental by the Splunk Threat Research team. This means we have not been able to test, simulate, or build datasets for this detection. Use at your own risk. This analytic is NOT supported.

Try in Splunk Security Cloud

Description

The following analytic detects the creation of a Scheduled Task with a high entropy, randomly generated name, leveraging Event ID 4698. It uses the ut_shannon function from the URL ToolBox Splunk application to measure the entropy of the Task Name. This activity is significant as adversaries often use randomly named Scheduled Tasks for lateral movement and remote code execution, employing tools like Impacket or CrackMapExec. If confirmed malicious, this could allow attackers to execute arbitrary code remotely, potentially leading to further compromise and persistence within the network.

  • Type: Hunting

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

  • Last Updated: 2024-05-28
  • Author: Mauricio Velazco, Splunk
  • ID: 9d22a780-5165-11ec-ad4f-3e22fbd008af

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1053 Scheduled Task/Job Execution, Persistence, Privilege Escalation
T1053.005 Scheduled Task Execution, Persistence, Privilege Escalation
Kill Chain Phase
  • Installation
  • Exploitation
NIST
  • DE.AE
CIS20
  • CIS 10
CVE 


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 `wineventlog_security` EventCode=4698 
| xmlkv Message 
| lookup ut_shannon_lookup word as Task_Name 
| where ut_shannon > 3 
| table  _time, dest, Task_Name, ut_shannon, Command, Author, Enabled, Hidden 
| `randomly_generated_scheduled_task_name_filter`

Macros

The SPL above uses the following Macros:

:information_source: randomly_generated_scheduled_task_name_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
  • Description
  • Command

How To Implement

To successfully implement this search, you need to be ingesting Windows Security Event Logs with 4698 EventCode enabled. The Windows TA as well as the URL ToolBox application are also required.

Known False Positives

Legitimate applications may use random Scheduled Task names.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
45.0 90 50 A windows scheduled task with a suspicious task name was created on $dest$

: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: 2