Suspicious New Module Module Added To IIS Server (via iis-configuration)

title: Suspicious New Module Module Added To IIS Server (via iis-configuration)
id: ecba592d-0a3e-590d-b292-5f2471862552
status: stable
description: This rule detects the addition of a new module to an IIS server.
references:
    - https://attack.mitre.org/techniques/T1505/004/
    - https://attack.mitre.org/techniques/T1685/001/
    - https://learn.microsoft.com/en-us/iis/manage/provisioning-and-managing-iis/configure-logging-in-iis
    - https://www.microsoft.com/en-us/security/blog/2022/12/12/iis-modules-the-evolution-of-web-shells-and-how-to-detect-them/
    - https://www.microsoft.com/en-us/security/blog/2022/07/26/malicious-iis-extensions-quietly-open-persistent-backdoors-into-servers/
    - https://learn.microsoft.com/en-us/iis/get-started/introduction-to-iis/iis-modules-overview
author: Huntrule Team
date: 2026-03-31
tags:
    - attack.persistence
    - attack.defense-impairment
    - attack.t1685.001
    - attack.t1505.004
logsource:
    product: windows
    service: iis-configuration
detection:
    selection:
        EventID: 29
        Configuration|contains: '/system.webServer/modules/add'
    filter_main_builtin:
        NewValue:
            - 'AnonymousAuthenticationModule'
            - 'CustomErrorModule'
            - 'DefaultDocumentModule'
            - 'DirectoryListingModule'
            - 'FileCacheModule'
            - 'HttpCacheModule'
            - 'HttpLoggingModule'
            - 'ProtocolSupportModule'
            - 'RequestFilteringModule'
            - 'StaticCompressionModule'
            - 'StaticFileModule'
            - 'TokenCacheModule'
            - 'UriCacheModule'
    filter_main_remove:
        NewValue: ''
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Unknown
level: medium