splunk_escuAnomaly

Powershell Windows Defender Exclusion Commands

The following analytic detects the use of PowerShell commands to add or set Windows Defender exclusions. It leverages EventCode 4104 to identify suspicious `Add-MpPreference` or `Set-MpPreference` commands with exclusion parameters. This activity is significant because adversaries often use it to bypass Windows Defender, allowing malicious code to execute without detection. If confirmed malicious, this behavior could enable attackers to evade antivirus defenses, maintain persistence, and execute further malicious activities undetected.

Detection Query

`powershell`
EventCode=4104
ScriptBlockText IN (
    "*Add-MpPreference *",
    "*Set-MpPreference *"
)
ScriptBlockText = "*-exclusion*"
| fillnull
| stats count min(_time) as firstTime
              max(_time) as lastTime
  by dest signature signature_id
     user_id vendor_product EventID
     Guid Opcode Name
     Path ProcessID ScriptBlockId
     ScriptBlockText
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| `powershell_windows_defender_exclusion_commands_filter`

Author

Teoderick Contreras, Splunk

Data Sources

Powershell Script Block Logging 4104

References

Raw Content

name: Powershell Windows Defender Exclusion Commands
id: 907ac95c-4dd9-11ec-ba2c-acde48001122
version: 17
creation_date: '2021-11-25'
modification_date: '2026-06-29'
author: Teoderick Contreras, Splunk
status: production
type: Anomaly
description: |-
    The following analytic detects the use of PowerShell commands to add or set Windows Defender exclusions.
    It leverages EventCode 4104 to identify suspicious `Add-MpPreference` or `Set-MpPreference` commands with exclusion parameters.
    This activity is significant because adversaries often use it to bypass Windows Defender, allowing malicious code to execute without detection.
    If confirmed malicious, this behavior could enable attackers to evade antivirus defenses, maintain persistence, and execute further malicious activities undetected.
data_source:
    - Powershell Script Block Logging 4104
search: |-
    `powershell`
    EventCode=4104
    ScriptBlockText IN (
        "*Add-MpPreference *",
        "*Set-MpPreference *"
    )
    ScriptBlockText = "*-exclusion*"
    | fillnull
    | stats count min(_time) as firstTime
                  max(_time) as lastTime
      by dest signature signature_id
         user_id vendor_product EventID
         Guid Opcode Name
         Path ProcessID ScriptBlockId
         ScriptBlockText
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `powershell_windows_defender_exclusion_commands_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. Also make sure that this registry was included in your config files ex. sysmon config to be monitored.
known_false_positives: admin or user may choose to use this windows features.
references:
    - https://tccontre.blogspot.com/2020/01/remcos-rat-evading-windows-defender-av.html
    - https://app.any.run/tasks/cf1245de-06a7-4366-8209-8e3006f2bfe5/
    - https://www.microsoft.com/security/blog/2022/01/15/destructive-malware-targeting-ukrainian-organizations/
drilldown_searches:
    - name: View the detection results for - "$user_id$" and "$dest$"
      search: '%original_detection_search% | search  user_id = "$user_id$" dest = "$dest$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$user_id$" and "$dest$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user_id$", "$dest$") | 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 suspicious powershell script with the ScriptBlockId [$ScriptBlockId$] containing exclusion commands to add or set Windows Defender exclusions was executed on host $dest$
        - field: user_id
          type: user
          score: 20
          message: A suspicious powershell script with the ScriptBlockId [$ScriptBlockId$] containing exclusion commands to add or set Windows Defender exclusions was executed on host $dest$ by user $user_id$
analytic_story:
    - CISA AA22-320A
    - AgentTesla
    - Remcos
    - Windows Defense Evasion Tactics
    - Data Destruction
    - WhisperGate
    - Warzone RAT
    - NetSupport RMM Tool Abuse
    - BlankGrabber Stealer
    - 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/powershell_windows_defender_exclusion_commands/windows-xml.log
          source: XmlWinEventLog:Microsoft-Windows-PowerShell/Operational
          sourcetype: XmlWinEventLog
      test_type: unit