Detection rules › Splunk
Windows New InProcServer32 Added
The following analytic detects the addition of new InProcServer32 registry keys on Windows endpoints. It leverages data from the Endpoint.Registry datamodel to identify changes in registry paths associated with InProcServer32. This activity is significant because malware often uses this mechanism to achieve persistence or execute malicious code by registering a new InProcServer32 key pointing to a harmful DLL. If confirmed malicious, this could allow an attacker to persist in the environment or execute arbitrary code, posing a significant threat to system integrity and security.
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Persistence | T1112 Modify Registry |
| Defense Impairment | T1112 Modify Registry |
Event coverage
| Provider | Event | Title |
|---|---|---|
| Sysmon | Event ID 13 | RegistryEvent (Value Set) |
Rule body splunk
name: Windows New InProcServer32 Added
id: 0fa86e31-0f73-4ec7-9ca3-dc88e117f1db
version: 9
creation_date: '2024-04-04'
modification_date: '2026-05-13'
author: Michael Haag, Splunk
status: production
type: Hunting
description: The following analytic detects the addition of new InProcServer32 registry keys on Windows endpoints. It leverages data from the Endpoint.Registry datamodel to identify changes in registry paths associated with InProcServer32. This activity is significant because malware often uses this mechanism to achieve persistence or execute malicious code by registering a new InProcServer32 key pointing to a harmful DLL. If confirmed malicious, this could allow an attacker to persist in the environment or execute arbitrary code, posing a significant threat to system integrity and security.
data_source:
- Sysmon EventID 13
search: '| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Registry where Registry.registry_path="*\\InProcServer32\\*" by Registry.registry_path Registry.registry_key_name Registry.registry_value_name Registry.registry_value_data Registry.dest Registry.process_guid Registry.user | `drop_dm_object_name(Registry)` |`security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `windows_new_inprocserver32_added_filter`'
how_to_implement: To successfully implement this search you need to be ingesting information on process that include the name of the process responsible for the changes from your endpoints into the `Endpoint` datamodel in the `Registry` node.
known_false_positives: False positives are expected. Filtering will be needed to properly reduce legitimate applications from the results.
references:
- https://www.netspi.com/blog/technical/red-team-operations/microsoft-outlook-remote-code-execution-cve-2024-21378/
analytic_story:
- Hellcat Ransomware
- Outlook RCE CVE-2024-21378
asset_type: Endpoint
cve:
- CVE-2024-21378
mitre_attack_id:
- T1112
product:
- Splunk Enterprise
- Splunk Enterprise Security
- Splunk Cloud
category: endpoint
security_domain: endpoint
tests:
- name: True Positive Test
attack_data:
- data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1566/cve-2024-21378/inprocserver32_windows-sysmon.log
sourcetype: XmlWinEventLog
source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
test_type: unit
Stages and Predicates
Stage 1: tstats
| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Registry where Registry.registry_path="*\\InProcServer32\\*" by Registry.registry_path Registry.registry_key_name Registry.registry_value_name Registry.registry_value_data Registry.dest Registry.process_guid Registry.user
Stage 2: search
| `drop_dm_object_name(Registry)`
Stage 3: search
| `security_content_ctime(firstTime)`
Stage 4: search
| `security_content_ctime(lastTime)`
Stage 5: search
| `windows_new_inprocserver32_added_filter`
Indicators
Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.
| Field | Kind | Values |
|---|---|---|
Registry.registry_path | eq |
|