Suspicious IIS Module Registration

SIGMA detection rule by Florian Roth (Nextron Systems), Microsoft (idea) · NOASSERTION

Detects a suspicious IIS module registration as described in Microsoft threat report on IIS backdoors

title: Suspicious IIS Module Registration
id: 043c4b8b-3a54-4780-9682-081cb6b8185c
status: test
description: Detects a suspicious IIS module registration as described in Microsoft threat report on IIS backdoors
references:
    - https://www.microsoft.com/security/blog/2022/07/26/malicious-iis-extensions-quietly-open-persistent-backdoors-into-servers/
author: Florian Roth (Nextron Systems), Microsoft (idea)
date: 2022-08-04
modified: 2023-01-23
tags:
    - attack.persistence
    - attack.t1505.004
logsource:
    category: process_creation
    product: windows
detection:
    selection_parent:
        ParentImage|endswith: '\w3wp.exe'
    selection_cli_1:
        CommandLine|contains: 'appcmd.exe add module'
    selection_cli_2:
        CommandLine|contains: ' system.enterpriseservices.internal.publish'
        Image|endswith: '\powershell.exe'
    selection_cli_3:
        CommandLine|contains|all:
            - 'gacutil'
            - ' /I'
    condition: selection_parent and 1 of selection_cli_*
falsepositives:
    - Administrative activity
level: high

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

314f0104-b1de-44d7-88ea-56443d609245

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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

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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.

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What do these messages mean?

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

[[ currentRule.title ]]

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