Previously Installed IIS Module Was Removed — Sigma Rule

Rule metadata and linked tags

Author: Nasreddine Bencherchali. Source status: test; severity: low. Source dates: 2024-10-06 / not supplied.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: ca39539ab4205dc1185b577e3c7e2a794cbac909df9996442d46672079de8247

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: Previously Installed IIS Module Was Removed
id: 9e1a1fdf-ee58-40ce-8e15-b66ca5a80e1f
status: test
description: Detects the removal of a previously installed IIS module.
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: Nasreddine Bencherchali
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/remove'
    condition: selection
falsepositives:
    - Legitimate administrator activity
# Note: Upgrade after an initial baseline
level: low

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