splunk-security_content/docs/_posts/2021-11-29-randomly_generated_scheduled_task_name.md

title, excerpt, categories, last_modified_at, toc, toc_label, tags

title	excerpt	categories	last_modified_at	toc	toc_label	tags
Randomly Generated Scheduled Task Name	Scheduled Task/Job, Scheduled Task	Endpoint	2021-11-29	true		Scheduled Task/Job Execution Persistence Privilege Escalation Scheduled Task Execution Persistence Privilege Escalation Splunk Enterprise Splunk Enterprise Security Splunk Cloud Endpoint

⚠️ WARNING THIS IS A EXPERIMENTAL DETECTION

We have not been able to test, simulate, or build datasets for this detection. Use at your own risk. This analytic is NOT supported.

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Description

The following hunting analytic leverages Event ID 4698, A scheduled task was created, to identify the creation of a Scheduled Task with a suspicious, high entropy, Task Name. To achieve this, this analytic also leverages the ut_shannon function from the URL ToolBox Splunk application. Red teams and adversaries alike may abuse the Task Scheduler to create and start a remote Scheduled Task and obtain remote code execution. To achieve this goal, tools like Impacket or Crapmapexec, typically create a Scheduled Task with a random task name on the victim host. This hunting analytic may help defenders identify Scheduled Tasks created as part of a lateral movement attack. The entropy threshold ut_shannon > 3 should be customized by users. The Command field can be used to determine if the task has malicious intent or not.

• Type: Hunting
• Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
• Datamodel: Endpoint
• Last Updated: 2021-11-29
• Author: Mauricio Velazco, Splunk
• ID: 9d22a780-5165-11ec-ad4f-3e22fbd008af

ATT&CK

ID	Technique	Tactic
T1053	Scheduled Task/Job	Execution, Persistence, Privilege Escalation

| T1053.005 | Scheduled Task | Execution, Persistence, Privilege Escalation |

Search

 `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`

Associated Analytic Story

• Active Directory Lateral Movement

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.

Required field

• _time
• dest
• Task_Name
• Description
• Command

Kill Chain Phase

• Privilege Escalation
• Lateral Movement
• Persistence

Known False Positives

Legitimate applications may use random Scheduled Task names.

RBA

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

Reference

• https://attack.mitre.org/techniques/T1053/005/
• https://splunkbase.splunk.com/app/2734/
• https://en.wikipedia.org/wiki/Entropy_(information_theory)

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

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