Detection: Malicious Powershell Executed As A Service

Updated Date: 2024-09-30 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.

Search

 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
Windows Event Log System 7045	Windows	`'xmlwineventlog'`	`'XmlWinEventLog:System'`

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

INC Ransom

Ke3chang

Moonstone Sleet

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: 5