Detection rules › Sigma
Amsi.DLL Load By Uncommon Process
Detects loading of Amsi.dll by uncommon processes
Known false positives
- Legitimate third party apps installed in "ProgramData" and "AppData" might generate some false positives. Apply additional filters accordingly
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Impact |
Telemetry coverage
| Provider | Record / event type |
|---|---|
| Sysmon | Event ID 7: Image loaded |
Rule body
title: Amsi.DLL Load By Uncommon Process
id: facd1549-e416-48e0-b8c4-41d7215eedc8
status: test
description: Detects loading of Amsi.dll by uncommon processes
references:
- https://infosecwriteups.com/amsi-bypass-new-way-2023-d506345944e9
- https://github.com/TheD1rkMtr/AMSI_patch
- https://github.com/surya-dev-singh/AmsiBypass-OpenSession
author: frack113
date: 2023-03-12
modified: 2026-06-29
tags:
- attack.impact
- attack.t1490
- detection.threat-hunting
logsource:
category: image_load
product: windows
detection:
selection:
ImageLoaded|endswith: '\amsi.dll'
filter_main_exact:
Image|endswith:
- ':\Windows\explorer.exe'
- ':\Windows\Sysmon64.exe'
- ':\Windows\Sysmon64a.exe'
filter_main_generic:
Image|contains:
- ':\Program Files (x86)\'
- ':\Program Files\'
- ':\Windows\System32\'
- ':\Windows\SysWOW64\'
- ':\Windows\WinSxS\'
filter_optional_defender:
Image|contains: ':\ProgramData\Microsoft\Windows Defender\Platform\'
Image|endswith: '\MsMpEng.exe'
filter_main_dotnet:
Image|contains:
- ':\Windows\Microsoft.NET\Framework\'
- ':\Windows\Microsoft.NET\Framework64\'
- ':\Windows\Microsoft.NET\FrameworkArm\'
- ':\Windows\Microsoft.NET\FrameworkArm64\'
Image|endswith: '\ngentask.exe'
filter_main_null:
Image: null
filter_main_empty:
Image: ''
condition: selection and not 1 of filter_main_* and not 1 of filter_optional_*
falsepositives:
- Legitimate third party apps installed in "ProgramData" and "AppData" might generate some false positives. Apply additional filters accordingly
level: low
Stages and Predicates
Stage 0: condition
selection and not 1 of filter_main_* and not 1 of filter_optional_*Stage 1: selection
selection:
ImageLoaded|endswith: '\amsi.dll'
Stage 2: not filter_main_*
filter_main_exact:
Image|endswith:
- ':\Windows\explorer.exe'
- ':\Windows\Sysmon64.exe'
- ':\Windows\Sysmon64a.exe'
filter_main_generic:
Image|contains:
- ':\Program Files (x86)\'
- ':\Program Files\'
- ':\Windows\System32\'
- ':\Windows\SysWOW64\'
- ':\Windows\WinSxS\'
filter_main_dotnet:
Image|contains:
- ':\Windows\Microsoft.NET\Framework\'
- ':\Windows\Microsoft.NET\Framework64\'
- ':\Windows\Microsoft.NET\FrameworkArm\'
- ':\Windows\Microsoft.NET\FrameworkArm64\'
Image|endswith: '\ngentask.exe'
filter_main_null:
Image: null
filter_main_empty:
Image: ''
Stage 3: not filter_optional_defender
filter_optional_defender:
Image|contains: ':\ProgramData\Microsoft\Windows Defender\Platform\'
Image|endswith: '\MsMpEng.exe'
Exclusions
The rule actively suppresses these predicates.
Indicators
These rows show field, operator, and value matches.
| Field | Kind | Values | Search |
|---|---|---|---|
ImageLoaded | ends_with |
| field:"ImageLoaded" kind:ends_with value:"\amsi.dll" |