Windows Impair Defense Set Win Defender Smart Screen Level To Warn

SPLUNK detection rule by Teoderick Contreras, Splunk · Apache-2.0

The following analytic detects modifications to the Windows registry that set the Windows Defender SmartScreen level to "warn." This detection leverages data from the Endpoint.Registry data model, specifically monitoring changes to the ShellSmartScreenLevel registry value. This activity is significant because altering SmartScreen settings to "warn" can reduce immediate suspicion from users, allowing potentially malicious executables to run with just a warning prompt. If confirmed malicious, this could enable attackers to execute harmful files, increasing the risk of successful malware deployment and subsequent system compromise.

name: Windows Impair Defense Set Win Defender Smart Screen Level To Warn
id: cc2a3425-2703-47e7-818f-3dca1b0bc56f
version: 11
creation_date: '2024-01-30'
modification_date: '2026-05-13'
author: Teoderick Contreras, Splunk
status: production
type: TTP
description: The following analytic detects modifications to the Windows registry that set the Windows Defender SmartScreen level to "warn." This detection leverages data from the Endpoint.Registry data model, specifically monitoring changes to the ShellSmartScreenLevel registry value. This activity is significant because altering SmartScreen settings to "warn" can reduce immediate suspicion from users, allowing potentially malicious executables to run with just a warning prompt. If confirmed malicious, this could enable attackers to execute harmful files, increasing the risk of successful malware deployment and subsequent system compromise.
data_source:
    - Sysmon EventID 13
search: '| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Registry where Registry.registry_path= "*\\Microsoft\\Windows\\System\\ShellSmartScreenLevel" Registry.registry_value_data="Warn" by Registry.action Registry.dest Registry.process_guid Registry.process_id Registry.registry_hive Registry.registry_path Registry.registry_key_name Registry.registry_value_data Registry.registry_value_name Registry.registry_value_type Registry.status Registry.user Registry.vendor_product | `drop_dm_object_name(Registry)` | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `windows_impair_defense_set_win_defender_smart_screen_level_to_warn_filter`'
how_to_implement: To successfully implement this search you need to be ingesting information on process that include the name of the process responsible for the changes from your endpoints into the `Endpoint` datamodel in the `Registry` node.
known_false_positives: It is unusual to turn this feature off a Windows system since it is a default security control, although it is not rare for some policies to disable it. Although no false positives have been identified, use the provided filter macro to tune the search.
references:
    - https://x.com/malmoeb/status/1742604217989415386?s=20
    - https://github.com/undergroundwires/privacy.sexy
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"
finding:
    title: Windows Defender SmartScreen Level to Warn on $dest$.
    entity:
        field: dest
        type: system
        score: 50
analytic_story:
    - Windows Defense Evasion Tactics
    - Windows Registry Abuse
asset_type: Endpoint
mitre_attack_id:
    - T1685
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/T1562.001/disable-windows-security-defender-features/windefender-bypas-2-sysmon.log
          source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
          sourcetype: XmlWinEventLog
      test_type: unit

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