Suspicious IIS Module Registration — Sigma Rule

Rule metadata and linked tags

Author: Florian Roth (Nextron Systems), Microsoft (idea). Source status: test; severity: high. Source dates: 2022-08-04 / 2023-01-23.

{
  "category": "process_creation",
  "product": "windows"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 80d9ab61b3c1cb1c03ba741a77ac6e41600e95dc81405969ce4c683035ecf4d5

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: 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

Original YAML and metadata in JSON

False positives

• Administrative activity

Source references

• https://www.microsoft.com/security/blog/2022/07/26/malicious-iis-extensions-quietly-open-persistent-backdoors-into-servers/