Malicious Powershell Executed As A Service

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Description

This detection is to identify the abuse the Windows SC.exe to execute malicious commands or payloads via PowerShell.

• Type: TTP

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

• Last Updated: 2021-04-07
• Author: Ryan Becwar
• ID: 8e204dfd-cae0-4ea8-a61d-e972a1ff2ff8

Annotations

ATT&CK

ATT&CK

ID	Technique	Tactic
T1569	System Services	Execution

T1569.002

Service Execution

Execution

Kill Chain Phase

• Installation

NIST

• DE.CM

CIS20

• CIS 10

CVE

Search

 `wineventlog_system` EventCode=7045 
| eval l_Service_File_Name=lower(Service_File_Name) 
| regex l_Service_File_Name="powershell[.\s]
|powershell_ise[.\s]
|pwsh[.\s]
|psexec[.\s]" 
| regex l_Service_File_Name="-nop[rofile\s]+
|-w[indowstyle]*\s+hid[den]*
|-noe[xit\s]+
|-enc[odedcommand\s]+" 
| stats count min(_time) as firstTime max(_time) as lastTime by EventCode Service_File_Name Service_Name Service_Start_Type Service_Type Service_Account user 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `malicious_powershell_executed_as_a_service_filter`

Macros

The SPL above uses the following Macros:

• wineventlog_system
• security_content_ctime

malicious_powershell_executed_as_a_service_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.

• EventCode
• Service_File_Name
• Service_Type
• _time
• Service_Name
• Service_Start_Type
• Service_Account
• user

How To Implement

To successfully implement this search, you need to be ingesting Windows System logs with the Service name, Service File Name Service Start type, and Service Type from your endpoints.

Known False Positives

Creating a hidden powershell service is rare and could key off of those instances.

Associated Analytic Story

• Malicious Powershell

RBA

Risk Score	Impact	Confidence	Message
72.0	90	80	Identifies the abuse the Windows SC.exe to execute malicious powerShell as a service $Service_File_Name$ by $user$ on $dest$

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

• https://www.fireeye.com/content/dam/fireeye-www/blog/pdfs/dosfuscation-report.pdf
• http://az4n6.blogspot.com/2017/
• https://www.danielbohannon.com/blog-1/2017/3/12/powershell-execution-argument-obfuscation-how-it-can-make-detection-easier

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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