Detection: Malicious Powershell Executed As A Service

Updated Date: 2024-05-20 ID: 8e204dfd-cae0-4ea8-a61d-e972a1ff2ff8 Author: Ryan Becwar Type: TTP Product: Splunk Enterprise Security

Description

The following analytic identifies the execution of malicious PowerShell commands or payloads via the Windows SC.exe utility. It detects this activity by analyzing Windows System logs (EventCode 7045) and filtering for specific PowerShell-related patterns in the ImagePath field. This behavior is significant because it indicates potential abuse of the Windows Service Control Manager to run unauthorized or harmful scripts, which could lead to system compromise. If confirmed malicious, this activity could allow attackers to execute arbitrary code, escalate privileges, or maintain persistence within the environment.

 1 `wineventlog_system` EventCode=7045 
 2| eval l_ImagePath=lower(ImagePath) 
 3| regex l_ImagePath="powershell[.\s]
 4|powershell_ise[.\s]
 5|pwsh[.\s]
 6|psexec[.\s]" 
 7| regex l_ImagePath="-nop[rofile\s]+
 8|-w[indowstyle]*\s+hid[den]*
 9|-noe[xit\s]+
10|-enc[odedcommand\s]+" 
11| stats count min(_time) as firstTime max(_time) as lastTime by EventCode ImagePath ServiceName StartType ServiceType AccountName UserID dest 
12| rename UserID as user
13| `security_content_ctime(firstTime)` 
14| `security_content_ctime(lastTime)` 
15| `malicious_powershell_executed_as_a_service_filter`

Data Source

Name Platform Sourcetype Source Supported App
Windows Event Log System 7045 Windows icon Windows 'xmlwineventlog' 'XmlWinEventLog:System' N/A

Macros Used

Name Value
security_content_ctime convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)
malicious_powershell_executed_as_a_service_filter search *
malicious_powershell_executed_as_a_service_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
T1569 System Services Execution
T1569.002 Service Execution Execution
KillChainPhase.INSTALLATION
NistCategory.DE_CM
Cis18Value.CIS_10
TeamTNT
APT32
APT38
APT39
APT41
Blue Mockingbird
Chimera
FIN6
Ke3chang
Silence
Wizard Spider

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 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

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
Identifies the abuse the Windows SC.exe to execute malicious powerShell as a service $ImagePath$ by $user$ on $dest$ 72 90 80
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 XmlWinEventLog:System XmlWinEventLog
Integration ✅ Passing Dataset XmlWinEventLog:System XmlWinEventLog

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: 3