Windows Registry COM Hijacking via scrobj.dll InprocServer32(Default) Persistence

Alerts on registry modifications setting InprocServer32(Default) to scrobj.dll, indicating possible COM hijacking persistence.

FreeReviewedSigma · Medium · v1

Product: windows
Category: registry_set
Author: frack113 (SigmaHQ), DRL 1.1
Published: 2022-08-20
Updated: 2026-07-30

Analysis Detection

ATT&CK techniques

Persistence → Priv Esc

Recon
Resource Dev
Initial Access
Execution
Persistence
- T1546.015Component Object Model Hijacking
Priv Esc
- T1546.015Component Object Model Hijacking
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags registry changes where the COM in-proc server for the default value is set to C:\WINDOWS\system32\scrobj.dll under an InprocServer32\(Default) target. COM Hijacking is a common persistence technique because it can redirect how Windows loads and instantiates COM components. The detection relies on registry set telemetry that captures the TargetObject ending pattern and the specific Details value pointing to scrobj.dll.

Reporting behind it

Related detections9 linkedT1546.015 — drag to rearrange

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Suspicious dllhost.exe Spawned with CLSID and Anomalous Parent (via process_creation)

Suspicious COM Handler Hijack of MsCtfMonitor CLSID via CharmingCypress

Malicious COM Hijack of PSFactoryBuffer InprocServer32

Malicious APT-C-60 COM Hijack via SpyGlace CLSID InProcServer32 (via registry_set)

Malicious COM Hijack via CLSID InProcServer32 Registry Modification (via registry_set)

Malicious COM Object Hijack Pointing to a User-Writable DLL (via registry_set)

Windows Registry COM Hijacking via scrobj.dll InprocServer32(Default) Persistence

Pivot detection · T1546.015 · 9 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

windows-registry-com-hijacking-via-scrobj-dll-inprocserver32-default-persistence-fe20dda1

title: Windows Registry COM Hijacking via scrobj.dll InprocServer32(Default) Persistence
id: ae7930bc-087a-4807-a8d0-b91bbac10ab7
status: test
description: This rule flags registry changes where the COM in-proc server for the default value is set to C:\WINDOWS\system32\scrobj.dll under an InprocServer32\(Default) target. COM Hijacking is a common persistence technique because it can redirect how Windows loads and instantiates COM components. The detection relies on registry set telemetry that captures the TargetObject ending pattern and the specific Details value pointing to scrobj.dll.
references:
  - https://github.com/redcanaryco/atomic-red-team/blob/40b77d63808dd4f4eafb83949805636735a1fd15/atomics/T1546.015/T1546.015.md
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/registry/registry_set/registry_set_persistence_scrobj_dll.yml
author: frack113, Huntrule Team
date: 2022-08-20
modified: 2023-08-17
tags:
  - attack.privilege-escalation
  - attack.persistence
  - attack.t1546.015
logsource:
  category: registry_set
  product: windows
detection:
  selection:
    TargetObject|endswith: InprocServer32\(Default)
    Details: C:\WINDOWS\system32\scrobj.dll
  condition: selection
falsepositives:
  - Legitimate use of the dll.
level: medium
license: DRL-1.1
related:
  - id: fe20dda1-6f37-4379-bbe0-a98d400cae90
    type: derived

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