Windows Impair Defense Disable Win Defender Compute File Hashes

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

The following analytic detects modifications to the Windows registry that disable Windows Defender's file hash computation by setting the EnableFileHashComputation value to 0. This detection leverages data from the Endpoint.Registry data model, focusing on changes to the specific registry path associated with Windows Defender. Disabling file hash computation can significantly impair Windows Defender's ability to detect and scan for malware, making it a critical behavior to monitor. If confirmed malicious, this activity could allow attackers to bypass Windows Defender, facilitating undetected malware execution and persistence in the environment.

name: Windows Impair Defense Disable Win Defender Compute File Hashes
id: fe52c280-98bd-4596-b6f6-a13bbf8ac7c6
version: 11
creation_date: '2024-01-29'
modification_date: '2026-05-13'
author: Teoderick Contreras, Splunk
status: production
type: TTP
description: The following analytic detects modifications to the Windows registry that disable Windows Defender's file hash computation by setting the EnableFileHashComputation value to 0. This detection leverages data from the Endpoint.Registry data model, focusing on changes to the specific registry path associated with Windows Defender. Disabling file hash computation can significantly impair Windows Defender's ability to detect and scan for malware, making it a critical behavior to monitor. If confirmed malicious, this activity could allow attackers to bypass Windows Defender, facilitating undetected malware execution and persistence in the environment.
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 Defender\\MpEngine\\EnableFileHashComputation" Registry.registry_value_data="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_win_defender_compute_file_hashes_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 File hashes computation set to disable 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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