Windows DLL Sideloading Suspected for ms<wbr>corsvc.dll via ImageLoad

Alerts on non-standard loads of msocrsvc.dll, a potential DLL sideloading opportunity on Windows.

FreeReviewedSigma · Medium · v2

Product: windows
Category: image_load
Author: Wietze Beukema (SigmaHQ), DRL 1.1
Published: 2024-07-11
Updated: 2026-07-31

ATT&CK techniques

Execution → Defense Evasion

Recon
Resource Dev
Initial Access
Execution
- T1574.001DLL
Persistence
- T1574.001DLL
Priv Esc
- T1574.001DLL
Defense Evasion
- T1574.001DLL
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags Windows processes that load a DLL path ending with mscorsvc.dll, then excludes common legitimate locations under Microsoft.NET Framework and WinSxS. Attackers may place a malicious DLL alongside an application or in a nonstandard directory so it is loaded during process startup. It relies on image load telemetry that records the loaded module filename and full path, matching the suffix and applying exclusions for typical framework and system locations.

Reporting behind it

Related detections9 linkedT1574.001 — drag to rearrange

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Windows DLL Sideloading Suspected for ms<wbr>corsvc.dll via ImageLoad

Pivot detection · T1574.001 · 9 related

Changelog

v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

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

windows-potential-dll-sideloading-via-loading-msocrsvc-dll-cdb15e19

title: Windows DLL Sideloading Suspected for ms<wbr>corsvc.dll via ImageLoad
id: a21ac530-1626-4687-95bc-3612fb45a000
status: test
description: This rule flags Windows processes that load a DLL path ending with mscorsvc.dll, then excludes common legitimate locations under Microsoft.NET Framework and WinSxS. Attackers may place a malicious DLL alongside an application or in a nonstandard directory so it is loaded during process startup. It relies on image load telemetry that records the loaded module filename and full path, matching the suffix and applying exclusions for typical framework and system locations.
references:
  - https://hijacklibs.net/entries/microsoft/built-in/mscorsvc.html
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/image_load/image_load_side_load_mscorsvc.yml
author: Wietze Beukema, Huntrule Team
date: 2024-07-11
modified: 2025-02-26
tags:
  - attack.privilege-escalation
  - attack.persistence
  - attack.execution
  - attack.stealth
  - attack.t1574.001
logsource:
  product: windows
  category: image_load
detection:
  selection:
    ImageLoaded|endswith: \mscorsvc.dll
  filter_main_generic:
    ImageLoaded|startswith:
      - C:\Windows\Microsoft.NET\Framework\
      - C:\Windows\Microsoft.NET\Framework64\
      - C:\Windows\Microsoft.NET\FrameworkArm\
      - C:\Windows\Microsoft.NET\FrameworkArm64\
      - C:\Windows\WinSxS\
  condition: selection and not 1 of filter_main_*
falsepositives:
  - Legitimate applications loading their own versions of the DLL mentioned in this rule.
level: medium
license: DRL-1.1
related:
  - id: cdb15e19-c2d0-432a-928e-e49c8c60dcf2
    type: derived

Convert

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