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Potential Persistence Via New AMSI Providers - Registry

Detects when an attacker adds a new AMSI provider via the Windows Registry to bypass AMSI (Antimalware Scan Interface) protections. Attackers may add custom AMSI providers to persist on the system and evade detection by security software that relies on AMSI for scanning scripts and other content. This technique is often used in conjunction with fileless malware and script-based attacks to maintain persistence while avoiding detection.

Detection Query

selection:
  TargetObject|contains:
    - \SOFTWARE\Microsoft\AMSI\Providers\
    - \SOFTWARE\WOW6432Node\Microsoft\AMSI\Providers\
filter_optional_avast:
  Image:
    - C:\Program Files\Avast Software\Avast\RegSvr.exe
    - C:\Program Files\Avast Software\Avast\x86\RegSvr.exe
  TargetObject|contains: \{FB904E4E-D2C7-4C8D-8492-B620BB9896B1}
filter_optional_avg:
  Image:
    - C:\Program Files\AVG\Antivirus\RegSvr.exe
    - C:\Program Files\AVG\Antivirus\x86\RegSvr.exe
  TargetObject|contains: \{FB904E4E-D2C7-4C8D-8492-B620BB9896B1}
filter_optional_avira:
  Image: C:\Program Files\Avira\Endpoint Protection SDK\endpointprotection.exe
  TargetObject|contains: \{00000001-3DCC-4B48-A82E-E2071FE58E05}
condition: selection and not 1 of filter_optional_*

Author

Nasreddine Bencherchali (Nextron Systems)

Created

2022-07-21

Data Sources

windowsRegistry Set Events

Platforms

windows

References

Tags

attack.persistence

Raw Content

title: Potential Persistence Via New AMSI Providers - Registry
id: 33efc23c-6ea2-4503-8cfe-bdf82ce8f705
status: test
description: |
    Detects when an attacker adds a new AMSI provider via the Windows Registry to bypass AMSI (Antimalware Scan Interface) protections.
    Attackers may add custom AMSI providers to persist on the system and evade detection by security software that relies on AMSI for scanning scripts and other content.
    This technique is often used in conjunction with fileless malware and script-based attacks to maintain persistence while avoiding detection.
references:
    - https://persistence-info.github.io/Data/amsi.html
    - https://github.com/gtworek/PSBits/blob/8d767892f3b17eefa4d0668f5d2df78e844f01d8/FakeAMSI/FakeAMSI.c
author: Nasreddine Bencherchali (Nextron Systems)
date: 2022-07-21
modified: 2025-10-26
tags:
    - attack.persistence
logsource:
    category: registry_set
    product: windows
detection:
    selection:
        TargetObject|contains:
            - '\SOFTWARE\Microsoft\AMSI\Providers\'
            - '\SOFTWARE\WOW6432Node\Microsoft\AMSI\Providers\'
    filter_optional_avast:
        Image:
            - 'C:\Program Files\Avast Software\Avast\RegSvr.exe'
            - 'C:\Program Files\Avast Software\Avast\x86\RegSvr.exe'
        TargetObject|contains: '\{FB904E4E-D2C7-4C8D-8492-B620BB9896B1}'
    filter_optional_avg:
        Image:
            - 'C:\Program Files\AVG\Antivirus\RegSvr.exe'
            - 'C:\Program Files\AVG\Antivirus\x86\RegSvr.exe'
        TargetObject|contains: '\{FB904E4E-D2C7-4C8D-8492-B620BB9896B1}'
    filter_optional_avira:
        Image: 'C:\Program Files\Avira\Endpoint Protection SDK\endpointprotection.exe'
        TargetObject|contains: '\{00000001-3DCC-4B48-A82E-E2071FE58E05}'
    condition: selection and not 1 of filter_optional_*
falsepositives:
    - Legitimate security products adding their own AMSI providers. Filter these according to your environment.
level: medium
regression_tests_path: regression_data/rules/windows/registry/registry_set/registry_set_persistence_amsi_providers/info.yml