Detection: Windows File and Directory Permissions Remove Inheritance

Description

The following analytic detects the removal of permission inheritance using ICACLS. This analytic identifies instances where ICACLS is used to remove permission inheritance from files or directories. The /inheritance:r flag, which strips inherited permissions while optionally preserving or altering explicit permissions, is monitored to detect changes that may restrict access or establish isolated permission configurations. Removing inheritance can be a legitimate administrative action but may also indicate an attempt to conceal malicious activity or bypass inherited security controls.

Search

 1
 2| tstats `security_content_summariesonly` min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Processes
 3  WHERE Processes.process_name IN( "icacls.exe", "cacls.exe", "xcacls.exe")
 4    AND
 5    Processes.process = "*/inheritance:r*"
 6  BY Processes.action Processes.dest Processes.original_file_name
 7     Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid
 8     Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path
 9     Processes.process Processes.process_exec Processes.process_guid
10     Processes.process_hash Processes.process_id Processes.process_integrity_level
11     Processes.process_name Processes.process_path Processes.user
12     Processes.user_id Processes.vendor_product
13
14| `drop_dm_object_name(Processes)`
15
16| `security_content_ctime(firstTime)`
17
18| `security_content_ctime(lastTime)`
19
20| `windows_file_and_directory_permissions_remove_inheritance_filter`

Data Source

Name	Platform	Sourcetype	Source
Windows Event Log Security 4688	Windows	'XmlWinEventLog'	'XmlWinEventLog:Security'
Sysmon EventID 1	Windows	'XmlWinEventLog'	'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'

Macros Used

Annotations

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Implementation

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.

Associated Analytic Story

• Crypto Stealer

Intermediate Findings

Threat Objects

References

• https://www.splunk.com/en_us/blog/security/-applocker-rules-as-defense-evasion-complete-analysis.html

Detection Testing

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

Source: GitHub | Version: 7