Uncommon New Firewall Rule Added In Windows Firewall Exception List — Sigma Rule

Rule metadata and linked tags

Author: frack113. Source status: test; severity: medium. Source dates: 2022-02-19 / 2025-10-08.

{
  "product": "windows",
  "service": "firewall-as"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 2efd8b38742e3f3b8f033899a652e323b9963399f8a485d15eb4949a2d56dc04

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: Uncommon New Firewall Rule Added In Windows Firewall Exception List
id: cde0a575-7d3d-4a49-9817-b8004a7bf105
status: test
description: Detects when a rule has been added to the Windows Firewall exception list
references:
    - https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2008-r2-and-2008/dd364427(v=ws.10)
author: frack113
date: 2022-02-19
modified: 2025-10-08
tags:
    - attack.defense-impairment
    - attack.t1686.003
logsource:
    product: windows
    service: firewall-as
detection:
    selection:
        EventID:
            - 2004 # A rule has been added to the Windows Defender Firewall exception list
            - 2071 # A rule has been added to the Windows Defender Firewall exception list. (Windows 11)
            - 2097
    filter_main_block:
        Action: 2 # Block
    filter_main_generic:
        ApplicationPath|startswith:
            - 'C:\Program Files (x86)\'
            - 'C:\Program Files\'
            - 'C:\Windows\System32\'
            - 'C:\Windows\SysWOW64\'
            - 'C:\Windows\WinSxS\'
    filter_main_covered_paths:
        # This filter is added to avoid duplicate alerting from 9e2575e7-2cb9-4da1-adc8-ed94221dca5e
        ApplicationPath|contains:
            - 'C:\PerfLogs\'
            - 'C:\Temp\'
            - 'C:\Tmp\'
            - 'C:\Users\Public\'
            - 'C:\Windows\Tasks\'
            - 'C:\Windows\Temp\'
            - '\AppData\Local\Temp\'
    filter_main_system_dllhost:
        ApplicationPath: 'System'
        ModifyingApplication: 'C:\Windows\System32\dllhost.exe'
    filter_main_tiworker:
        ModifyingApplication|startswith: 'C:\Windows\WinSxS\'
        ModifyingApplication|endswith: '\TiWorker.exe'
    filter_main_null:
        ApplicationPath: null
    filter_optional_no_path:
        # This filter filters a lot of FPs related to Windows Services
        ModifyingApplication:
            - 'C:\Windows\System32\svchost.exe'
            - 'C:\Windows\System32\dllhost.exe'
        ApplicationPath: ''
    filter_optional_msmpeng:
        - ModifyingApplication|startswith:
              - 'C:\ProgramData\Microsoft\Windows Defender\Platform\'
              - 'C:\Program Files\Windows Defender\'
          ModifyingApplication|endswith: '\MsMpEng.exe'
        - ApplicationPath|startswith:
              - 'C:\ProgramData\Microsoft\Windows Defender\Platform\'
              - 'C:\Program Files\Windows Defender\'
          ApplicationPath|endswith: '\MsMpEng.exe'
    condition: selection and not 1 of filter_main_* and not 1 of filter_optional_*
level: medium

Original YAML and metadata in JSON

False positives

No reviewed association in this snapshot.

Source references

• https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2008-r2-and-2008/dd364427(v=ws.10)