Detection: Powershell COM Hijacking InprocServer32 Modification

Description

The following analytic detects attempts to modify or add a Component Object Model (COM) entry to the InProcServer32 path within the registry using PowerShell. It leverages PowerShell ScriptBlock Logging (EventCode 4104) to identify suspicious script blocks that target the InProcServer32 registry path. This activity is significant because modifying COM objects can be used for persistence or privilege escalation by attackers. If confirmed malicious, this could allow an attacker to execute arbitrary code or maintain persistent access to the compromised system, posing a severe security risk.

Search

1`powershell` EventCode=4104 ScriptBlockText = "*Software\\Classes\\CLSID\\*\\InProcServer32*" 
2| stats count min(_time) as firstTime max(_time) as lastTime by EventCode ScriptBlockText Computer UserID 
3| `security_content_ctime(firstTime)` 
4| `security_content_ctime(lastTime)` 
5| `powershell_com_hijacking_inprocserver32_modification_filter`

Data Source

Name	Platform	Sourcetype	Source	Supported App
Powershell Script Block Logging 4104	Windows	'xmlwineventlog'	'XmlWinEventLog:Microsoft-Windows-PowerShell/Operational'	N/A

Macros Used

Annotations

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Implementation

The following analytic requires PowerShell operational logs to be imported. Modify the PowerShell macro as needed to match the sourcetype or add index. This analytic is specific to 4104, or PowerShell Script Block Logging.

Known False Positives

False positives will be present if any scripts are adding to inprocserver32. Filter as needed.

Associated Analytic Story

• Malicious PowerShell

Risk Based Analytics (RBA)

References

• https://attack.mitre.org/techniques/T1546/015/

• https://www.splunk.com/en_us/blog/security/hunting-for-malicious-powershell-using-script-block-logging.html

• https://blog.cluster25.duskrise.com/2022/09/23/in-the-footsteps-of-the-fancy-bear-powerpoint-graphite/

• https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1546.015/T1546.015.md

Detection Testing

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: 2