Msiexec.exe Loads a DLL and Calls DllUnregisterServer via /z
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
- 2026-10-21
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 identifies executions where msiexec.exe loads a DLL and the command-line indicates use of the /z option together with a .dll argument. It matters because invoking DLL entry-point style functionality through installer components can be used for stealthy code execution. The detection relies on Windows process creation telemetry, matching msiexec.exe in image/original filename and filtering on specific command-line patterns.
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
Changelog
v4- v4Candidate ingested via manual entry.2026-10-21
- v1No 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.
title: Msiexec.exe Loads a DLL and Calls DllUnregisterServer via /z
id: 0b05c0a9-2930-4b6e-84c4-ba8d73f4f012
status: test
description: This rule identifies executions where msiexec.exe loads a DLL and the command-line indicates use of the /z option together with a .dll argument. It matters because invoking DLL entry-point style functionality through installer components can be used for stealthy code execution. The detection relies on Windows process creation telemetry, matching msiexec.exe in image/original filename and filtering on specific command-line patterns.
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: 2026-10-19
tags:
- attack.stealth
- attack.t1218.007
logsource:
product: windows
category: process_creation
detection:
selection_img:
- Image|endswith: \msiexec.exe
- OriginalFileName: \msiexec.exe
selection_cli:
CommandLine|contains|windash: " -z "
CommandLine|contains: .dll
filter_optional_msihandler:
CommandLine|endswith: \MsiExec.exe" /Z "C:\Windows\CCM\MsiHandler.dll"
condition: all of selection_* and not 1 of filter_optional_*
falsepositives:
- Unknown
level: medium
regression_tests_path: regression_data/rules/windows/process_creation/proc_creation_win_msiexec_dll/info.yml
license: DRL-1.1
related:
- id: 84f52741-8834-4a8c-a413-2eb2269aa6c8
type: derived