Windows Firewall Rule Added

name: Windows Firewall Rule Added
id: efc25501-4e75-4075-8cc5-ac80f2847d80
version: 9
creation_date: '2025-03-21'
modification_date: '2026-06-08'
author: Teoderick Contreras, Splunk
status: production
type: Anomaly
description: This detection identifies instances where a Windows Firewall rule is added by monitoring Event ID 4946 in the Windows Security Event Log. Firewall rule modifications can indicate legitimate administrative actions, but they may also signal unauthorized changes, misconfigurations, or malicious activity such as attackers allowing traffic for backdoors or persistence mechanisms. By analyzing fields like RuleName, RuleId, Computer, and ProfileChanged, security teams can determine whether the change aligns with expected behavior. Correlating with user activity and process execution can help distinguish false positives from real threats, ensuring better visibility into potential security risks.
data_source:
    - Windows Event Log Security 4946
search: |-
    `wineventlog_security` EventCode=4946
      | stats count min(_time) as firstTime max(_time) as lastTime
        BY RuleName signature subject
           status dest ProcessID
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `windows_firewall_rule_added_filter`
how_to_implement: This detection is based on data collected from Endpoint Detection and Response (EDR) agents, which provide security-related telemetry from monitored endpoints. Specifically, it focuses on Windows Security Event Log entries with EventID 4946, which indicates that a new Windows Firewall rule has been added. To implement this detection in Splunk, you must ingest Windows Security Event Logs that capture EventID 4946, ensuring that critical fields such as _time, EventRecordID, ProcessID, ThreadID, Computer, ProfileChanged, RuleName, and RuleId are available for analysis. These logs must be processed using the appropriate Splunk Technology Add-ons (TAs) to ensure compatibility with the EDR product and proper field extraction. Additionally, mapping these logs to the appropriate data model, such as the Endpoint data model, enhances structured analysis. Leveraging the Splunk Common Information Model (CIM) helps normalize field names, ensuring consistency across different data sources. By implementing this approach, you can effectively detect and monitor Windows Firewall rule modifications, providing visibility into potential security risks or unauthorized changes.
known_false_positives: Legitimate admin changes, Group Policy updates, software installs, security tools, and automated scripts can trigger false positives for Event ID 4946.
references:
    - https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-10/security/threat-protection/auditing/event-4946
drilldown_searches:
    - name: View the detection results for - "$dest$"
      search: '%original_detection_search% | search  dest = "$dest$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$dest$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: 7d
      latest_offset: "0"
intermediate_findings:
    entities:
        - field: dest
          type: system
          score: 20
          message: a new firewall rule $RuleName$ added on $dest$.
analytic_story:
    - ShrinkLocker
    - Medusa Ransomware
    - NetSupport RMM Tool Abuse
    - Salat Stealer
asset_type: Endpoint
mitre_attack_id:
    - T1686
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1562.004/firewall_win_event/added_rule/MPSSVC_Rule-Level_Policy_Change-4946.log
          source: XmlWinEventLog:Security
          sourcetype: XmlWinEventLog
      test_type: unit