sigmalowHunting

Amsi.DLL Load By Uncommon Process

Detects loading of Amsi.dll by uncommon processes

MITRE ATT&CK

impact

Detection Query

selection:
  ImageLoaded|endswith: \amsi.dll
filter_main_exact:
  Image|endswith:
    - :\Windows\explorer.exe
    - :\Windows\Sysmon64.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_*

Author

frack113

Created

2023-03-12

Data Sources

windowsImage Load Events

Platforms

windows

References

Tags

attack.impactattack.t1490detection.threat-hunting

Raw Content

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: 2025-02-24
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'
    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