Windows Impair Defense Disable Web Evaluation

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

The following analytic detects modifications to the Windows registry entry "EnableWebContentEvaluation" to disable Windows Defender web content evaluation. It leverages data from the Endpoint.Registry datamodel, specifically monitoring changes where the registry value is set to "0x00000000". This activity is significant as it indicates an attempt to impair browser security features, potentially allowing malicious web content to bypass security checks. If confirmed malicious, this could lead to users interacting with harmful scripts or unsafe web elements, increasing the risk of system exploitation and security breaches.

name: Windows Impair Defense Disable Web Evaluation
id: e234970c-dcf5-4f80-b6a9-3a562544ca5b
version: 13
creation_date: '2024-01-29'
modification_date: '2026-06-08'
author: Teoderick Contreras, Splunk
status: production
type: TTP
description: The following analytic detects modifications to the Windows registry entry "EnableWebContentEvaluation" to disable Windows Defender web content evaluation. It leverages data from the Endpoint.Registry datamodel, specifically monitoring changes where the registry value is set to "0x00000000". This activity is significant as it indicates an attempt to impair browser security features, potentially allowing malicious web content to bypass security checks. If confirmed malicious, this could lead to users interacting with harmful scripts or unsafe web elements, increasing the risk of system exploitation and security breaches.
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= "*\\Windows\\CurrentVersion\\AppHost\\EnableWebContentEvaluation"  AND
           Registry.registry_value_data IN (0, "0x00000000")
           )
           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_disable_web_evaluation_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 web content evaluation feature set to disable on $dest$.
    entity:
        field: dest
        type: system
        score: 50
analytic_story:
    - Windows Defense Evasion Tactics
    - Windows Registry Abuse
    - Salat Stealer
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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522ac381-0d49-4965-a312-aa54cac2ff5c

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