Windows File and Directory Enable ReadOnly Permissions

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

The following analytic detects instances where file or folder permissions are modified to grant read-only access. Such changes are characterized by the presence of read-related permissions (e.g., R, REA, RA, RD) and the absence of write (W) or execute (E) permissions. Monitoring these events is crucial for tracking access control changes that could be intentional for restricting access or indicative of malicious behavior. Alerts generated by this detection help ensure that legitimate security measures are enforced while unauthorized changes are promptly investigated.

name: Windows File and Directory Enable ReadOnly Permissions
id: 1ae407b0-a042-4eb0-834a-590da055575e
version: 7
creation_date: '2023-04-12'
modification_date: '2026-05-13'
author: Teoderick Contreras, Splunk
status: production
type: TTP
description: The following analytic detects instances where file or folder permissions are modified to grant read-only access. Such changes are characterized by the presence of read-related permissions (e.g., R, REA, RA, RD) and the absence of write (W) or execute (E) permissions. Monitoring these events is crucial for tracking access control changes that could be intentional for restricting access or indicative of malicious behavior. Alerts generated by this detection help ensure that legitimate security measures are enforced while unauthorized changes are promptly investigated.
data_source:
    - Sysmon EventID 1
    - Windows Event Log Security 4688
search: '| tstats `security_content_summariesonly` min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.process_name IN( "icacls.exe", "cacls.exe", "xcacls.exe") AND Processes.process IN ("*/grant*", "*/G*") AND Processes.process IN ("*SYSTEM*", "*admin*", "*S-1-1-0*", "*EVERYONE*") 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)` | rex field=process ":\\((?<permission>[^)]+)\\)" | eval has_read_attribute=if(match(permission, "R"), "true", "false") | eval has_write_execute=if(match(permission, "(W|GA|X|M|F|AD|DC|DE)"), "true", "false") | where has_write_execute="false" and has_read_attribute = "true" | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `windows_file_and_directory_enable_readonly_permissions_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 GUID, process name, and parent process. 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: Administrators or administrative scripts may use this application. Filter as needed.
references:
    - https://www.splunk.com/en_us/blog/security/-applocker-rules-as-defense-evasion-complete-analysis.html
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: A [$process_name$] was executed on [$dest$] attempting to change the access to a file or directory into readonly permissions.
    entity:
        field: dest
        type: system
        score: 50
threat_objects:
    - field: process_name
      type: process_name
analytic_story:
    - Crypto Stealer
    - NetSupport RMM Tool Abuse
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/icacls_inheritance/icacls_process_1.log
          source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
          sourcetype: XmlWinEventLog
      test_type: unit

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Format & documentation suggestions

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