Windows msiexec.exe Command Line Loading a DLL and Calling DllUnregisterServer
Alert when msiexec.exe runs with -z and a .dll on the command line, consistent with DLL DllUnregisterServer execution.
- Product
- windows
- Category
- process_creation
- Author
- frack113 (SigmaHQ), DRL 1.1
- Published
- 2022-04-24
- Updated
- 2026-07-30
ATT&CK techniques
Defense EvasionRecon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact
What it detects
This rule flags process creation events where msiexec.exe is executed with arguments indicating the -z option and includes a .dll path in the command line. It is consistent with a technique where msiexec loads a DLL and invokes its DllUnregisterServer functionality, which can support stealthy execution by abusing legitimate installer behavior. The detection relies on process creation telemetry capturing msiexec.exe identification and the raw command line contents.
Reporting behind it
- github.comhttps://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1218.007/T1218.007.md
- lolbas-project.github.iohttps://lolbas-project.github.io/lolbas/Binaries/Msiexec/
- twitter.comhttps://twitter.com/_st0pp3r_/status/1583914515996897281
- github.comhttps://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_msiexec_dll.yml
Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.
title: Windows msiexec.exe Command Line Loading a DLL and Calling DllUnregisterServer
id: 0b05c0a9-2930-4b6e-84c4-ba8d73f4f012
status: test
description: This rule flags process creation events where msiexec.exe is executed with arguments indicating the -z option and includes a .dll path in the command line. It is consistent with a technique where msiexec loads a DLL and invokes its DllUnregisterServer functionality, which can support stealthy execution by abusing legitimate installer behavior. The detection relies on process creation telemetry capturing msiexec.exe identification and the raw command line contents.
references:
- https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1218.007/T1218.007.md
- https://lolbas-project.github.io/lolbas/Binaries/Msiexec/
- https://twitter.com/_st0pp3r_/status/1583914515996897281
- https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_msiexec_dll.yml
author: frack113, Huntrule Team
date: 2022-04-24
modified: 2024-03-13
tags:
- attack.stealth
- attack.t1218.007
logsource:
product: windows
category: process_creation
detection:
selection_img:
- Image|endswith: \msiexec.exe
- OriginalFileName: \msiexec.exe
selection_flag:
CommandLine|contains|windash: " -z "
selection_dll:
CommandLine|contains: .dll
condition: all of selection_*
falsepositives:
- Unknown
level: medium
license: DRL-1.1
related:
- id: 84f52741-8834-4a8c-a413-2eb2269aa6c8
type: derived