Windows SubInAcl Execution

SPLUNK detection rule by Nasreddine Bencherchali, Michael Haag, Splunk · Apache-2.0

The following analytic detects the execution of the SubInAcl utility. SubInAcl is a legacy Windows Resource Kit tool from the Windows 2003 era, used to manipulate security descriptors of securable objects. It leverages data from Endpoint Detection and Response (EDR) agents, specifically searching for any process execution involving "SubInAcl.exe" binary. This activity can be significant because the utility should be rarely found on modern Windows machines, which mean any execution could potentially be considered suspicious. If confirmed malicious, this could allow an attacker to blind defenses by tampering with EventLog ACLs or modifying the access to a previously denied resource.

name: Windows SubInAcl Execution
id: 12491419-1a6f-4af4-afc3-4e2052f0610e
version: 9
creation_date: '2020-04-29'
modification_date: '2026-05-13'
author: Nasreddine Bencherchali, Michael Haag, Splunk
status: production
type: Anomaly
description: The following analytic detects the execution of the SubInAcl utility. SubInAcl is a legacy Windows Resource Kit tool from the Windows 2003 era, used to manipulate security descriptors of securable objects. It leverages data from Endpoint Detection and Response (EDR) agents, specifically searching for any process execution involving "SubInAcl.exe" binary. This activity can be significant because the utility should be rarely found on modern Windows machines, which mean any execution could potentially be considered suspicious. If confirmed malicious, this could allow an attacker to blind defenses by tampering with EventLog ACLs or modifying the access to a previously denied resource.
data_source:
    - Sysmon EventID 1
    - Windows Event Log Security 4688
    - CrowdStrike ProcessRollup2
search: |-
    | tstats `security_content_summariesonly` values(Processes.process) as process min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Processes
      WHERE (
            Processes.process_name=subinacl.exe
            OR
            Processes.original_file_name=SubInAcl.exe
        )
      BY Processes.action Processes.dest Processes.original_file_name
         Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid
         Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path
         Processes.process Processes.process_exec Processes.process_guid
         Processes.process_hash Processes.process_id Processes.process_integrity_level
         Processes.process_name Processes.process_path Processes.user
         Processes.user_id Processes.vendor_product
    | `drop_dm_object_name(Processes)`
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `windows_subinacl_execution_filter`
how_to_implement: The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process name, and process original file name. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the `Processes` node of the `Endpoint` data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.
known_false_positives: No false positives have been identified at this time. should be identified and understood.
references:
    - https://www.pwc.com/gx/en/issues/cybersecurity/cyber-threat-intelligence/cyber-year-in-retrospect/yir-cyber-threats-report-download.pdf
    - https://attack.mitre.org/techniques/T1222/001/
drilldown_searches:
    - name: View the detection results for - "$user$" and "$dest$"
      search: '%original_detection_search% | search  user = "$user$" dest = "$dest$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$user$" and "$dest$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$", "$dest$") | 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: user
          type: user
          score: 20
          message: An instance of $parent_process_name$ spawning $process_name$ was identified attempting to disable security services on endpoint $dest$ by user $user$.
        - field: dest
          type: system
          score: 20
          message: An instance of $parent_process_name$ spawning $process_name$ was identified attempting to disable security services on endpoint $dest$ by user $user$.
threat_objects:
    - field: process_name
      type: process_name
analytic_story:
    - Defense Evasion or Unauthorized Access Via SDDL Tampering
asset_type: Endpoint
mitre_attack_id:
    - T1222.001
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/T1222.001/subinacl/subinacl_sysmon.log
          source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
          sourcetype: XmlWinEventLog
      test_type: unit

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

62e101a9-8646-4be9-b192-4eb3cd59c014

Propose edits, view related rules, and engage with the community through comments.

Executable code, not a declarative rule

This submission is arbitrary [[ currentRule.format ? currentRule.format.toUpperCase() : '' ]] code, not a declarative detection rule — review it as you would any script before running it, and note that it cannot be safely aggregated or auto-executed alongside YARA/Sigma/Suricata/CRS rules.

Rejected pattern present

[[ reason ]]

What does this mean?

Format & documentation suggestions

Not a security issue — this rule is valid and was accepted as-is. These are optional fields/conventions its own format recommends, mainly affecting its quality score and how well it documents itself for other reviewers.

[[ reason ]]

What do these messages mean?

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

[[ currentRule.title ]]

Community Discussion