New Module Module Added To IIS Server — Sigma Rule

Rule metadata and linked tags

Author: frack113. Source status: test; severity: medium. Source dates: 2024-10-06 / not supplied.

{
  "product": "windows",
  "service": "iis-configuration"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 6aadc1c7021c1283e184025a184e53d71a7cf42c7c8d185ea6fa2e8db6569042

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: New Module Module Added To IIS Server
id: dd857d3e-0c6e-457b-9b48-e82ae7f86bd7
status: test
description: Detects the addition of a new module to an IIS server.
references:
    - 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: frack113
date: 2024-10-06
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:
    - Legitimate administrator activity
level: medium

Original YAML and metadata in JSON

False positives

• Legitimate administrator activity

Source references

• 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