Windows IIS Configuration: New Module Added to /system.webServer/modules
Flags IIS configuration events where a new module is added under /system.webServer/modules.
- Product
- windows
- Service
- iis-configuration
- Author
- frack113 (SigmaHQ), DRL 1.1
- Published
- 2024-10-06
- Updated
- 2026-07-31
ATT&CK techniques
PersistenceRecon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact
What it detects
This rule identifies IIS configuration changes where a new module is added under /system.webServer/modules. Attackers can persist or enable unwanted behavior by installing custom IIS modules, so alerting on unexpected additions helps detect defense-impairment and persistence attempts. It relies on IIS configuration change telemetry, specifically EventID 29 with a configuration payload containing /system.webServer/modules/add, and filters out a set of known module values.
Reporting behind it
- learn.microsoft.comhttps://learn.microsoft.com/en-us/iis/manage/provisioning-and-managing-iis/configure-logging-in-iis
- microsoft.comhttps://www.microsoft.com/en-us/security/blog/2022/12/12/iis-modules-the-evolution-of-web-shells-and-how-to-detect-them/
- microsoft.comhttps://www.microsoft.com/en-us/security/blog/2022/07/26/malicious-iis-extensions-quietly-open-persistent-backdoors-into-servers/
- learn.microsoft.comhttps://learn.microsoft.com/en-us/iis/get-started/introduction-to-iis/iis-modules-overview
- github.comhttps://github.com/SigmaHQ/sigma/blob/master/rules/windows/builtin/iis-configuration/win_iis_module_added.yml
Changelog
v2- v2Candidate ingested via manual entry.2026-07-31
- v1No changelog recorded for this version.2026-07-30
Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.
title: "Windows IIS Configuration: New Module Added to /system.webServer/modules"
id: 22158dce-90d8-4591-b1e6-71e764e951e9
status: test
description: This rule identifies IIS configuration changes where a new module is added under /system.webServer/modules. Attackers can persist or enable unwanted behavior by installing custom IIS modules, so alerting on unexpected additions helps detect defense-impairment and persistence attempts. It relies on IIS configuration change telemetry, specifically EventID 29 with a configuration payload containing /system.webServer/modules/add, and filters out a set of known module values.
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
- https://github.com/SigmaHQ/sigma/blob/master/rules/windows/builtin/iis-configuration/win_iis_module_added.yml
author: frack113, Huntrule Team
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
license: DRL-1.1
related:
- id: dd857d3e-0c6e-457b-9b48-e82ae7f86bd7
type: derived