New Module Module Added To IIS Server

SIGMA detection rule by frack113 · NOASSERTION

Detects the addition of a new module to an IIS server.

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

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

368c54b6-d934-4908-b586-5e9821bd4767

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Executable code, not a declarative rule

This submission is arbitrary [[ currentRule.format ? currentRule.format.toUpperCase() : '' ]] code, not a declarative detection rule — review it as you would any script before running it, and note that it cannot be safely aggregated or auto-executed alongside YARA/Sigma/Suricata/CRS rules.

Rejected pattern present

[[ reason ]]

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Format & documentation suggestions

Not a security issue — this rule is valid and was accepted as-is. These are optional fields/conventions its own format recommends, mainly affecting its quality score and how well it documents itself for other reviewers.

[[ reason ]]

What do these messages mean?

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

[[ currentRule.title ]]

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