windows_defender_asr_rule_disabled.yml

name: Windows Defender ASR Rule Disabled
id: 429d611b-3183-49a7-b235-fc4203c4e1cb
version: 1
date: '2023-11-27'
author: Michael Haag, Splunk
status: production
type: TTP
data_source:
- Windows Event Log Defender 5007
description: 'The following analytic identifies when a Windows Defender ASR rule disabled events. ASR is a feature of Windows Defender Exploit Guard that prevents actions and apps that are typically used by exploit-seeking malware to infect machines. ASR rules are applied to processes and applications. When a process or application attempts to perform an action that is blocked by an ASR rule, an event is generated. This detection searches for ASR rule disabled events that are generated when an ASR rule is disabled.'
search: '`ms_defender` EventCode IN (5007) 
  | rex field=New_Value "0x(?<New_Registry_Value>\\d+)$"
  | rex field=Old_Value "0x(?<Old_Registry_Value>\\d+)$"
  | rex field=New_Value "Rules\\\\(?<ASR_ID>[A-Fa-f0-9\\-]+)\\s*="
  | lookup asr_rules ID AS ASR_ID OUTPUT ASR_Rule
  | eval New_Registry_Value=case(New_Registry_Value=="0", "Disabled", New_Registry_Value=="1", "Block", New_Registry_Value=="2", "Audit", New_Registry_Value=="6", "Warn")
  | eval Old_Registry_Value=case(Old_Registry_Value=="0", "Disabled", Old_Registry_Value=="1", "Block", Old_Registry_Value=="2", "Audit", Old_Registry_Value=="6", "Warn")
  | search New_Registry_Value="Disabled"
  | stats count min(_time) as firstTime max(_time) as lastTime by host, New_Value, Old_Value, Old_Registry_Value, New_Registry_Value, ASR_Rule
  | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`| rename host as dest | `windows_defender_asr_rule_disabled_filter`'
how_to_implement: The following analytic requires collection of Windows Defender Operational logs in either XML or multi-line. To collect, setup a new input for the Windows Defender Operational logs. In addition, it does require a lookup that maps the ID to ASR Rule name.
known_false_positives: False positives may occur if applications are typically disabling ASR rules in the environment. Monitor for changes to ASR rules to determine if this is a false positive.
references:
- https://asrgen.streamlit.app/
tags:
  analytic_story:
  - Windows Attack Surface Reduction
  asset_type: Endpoint
  atomic_guid: []
  confidence: 100
  impact: 100
  message: ASR rule disabled event, $ASR_Rule$, was triggered on $dest$.
  mitre_attack_id:
  - T1112
  observable:
  - name: ASR_Rule
    type: Unknown
    role:
    - Other
  - name: dest
    type: Endpoint
    role:
    - Victim
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  risk_score: 100
  required_fields:
  - host
  - New_Value
  - Old_Value
  - Old_Registry_Value
  - New_Registry_Value
  - ASR_Rule
  security_domain: endpoint
tests:
- name: True Positive Test
  attack_data:
  - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1059/defender/asr_disabled_registry.log
    source: WinEventLog:Microsoft-Windows-Windows Defender/Operational
    sourcetype: xmlwineventlog