Detection: Malicious InProcServer32 Modification

Updated Date: 2024-11-13 ID: 127c8d08-25ff-11ec-9223-acde48001122 Author: Michael Haag, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects a process modifying the registry with a known malicious CLSID under InProcServer32. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on registry modifications within the HKLM or HKCU Software Classes CLSID paths. This activity is significant as it may indicate an attempt to load a malicious DLL, potentially leading to code execution. If confirmed malicious, this could allow an attacker to persist in the environment, execute arbitrary code, or escalate privileges, posing a severe threat to system integrity and security.

1
2| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Registry where Registry.registry_path="*\\CLSID\\{89565275-A714-4a43-912E-978B935EDCCC}\\InProcServer32\\(Default)" by Registry.action Registry.dest Registry.process_guid Registry.process_id Registry.registry_hive Registry.registry_path Registry.registry_key_name Registry.registry_value_data Registry.registry_value_name Registry.registry_value_type Registry.status Registry.user Registry.vendor_product 
3| `drop_dm_object_name(Registry)` 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `malicious_inprocserver32_modification_filter`

Data Source

Name Platform Sourcetype Source
Sysmon EventID 12 Windows icon Windows 'xmlwineventlog' 'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'
Sysmon EventID 13 Windows icon Windows 'xmlwineventlog' 'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'

Macros Used

Name Value
security_content_ctime convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)
malicious_inprocserver32_modification_filter search *
malicious_inprocserver32_modification_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
T1218.010 Regsvr32 Defense Evasion
T1112 Modify Registry Defense Evasion
Exploitation
DE.CM
CIS 10

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

The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the Processes node of the Endpoint data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.

Known False Positives

False positives should be limited, filter as needed. In our test case, Remcos used regsvr32.exe to modify the registry. It may be required, dependent upon the EDR tool producing registry events, to remove (Default) from the command-line.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

A process identified on endpoint $dest$ modifying the registry with a known malicious clsid under InProcServer32.

Risk Object Risk Object Type Risk Score Threat Objects
dest system 80 No Threat Objects

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset XmlWinEventLog:Microsoft-Windows-Sysmon/Operational XmlWinEventLog
Integration ✅ Passing Dataset XmlWinEventLog:Microsoft-Windows-Sysmon/Operational 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: 6