Detection: Icacls Deny Command

Updated Date: 2025-06-17 ID: cf8d753e-a8fe-11eb-8f58-acde48001122 Author: Teoderick Contreras, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic detects instances where an adversary modifies security permissions of a file or directory using commands like "icacls.exe", "cacls.exe", or "xcacls.exe" with deny options. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on process names and command-line executions. This activity is significant as it is commonly used by Advanced Persistent Threats (APTs) and coinminer scripts to evade detection and impede access to critical files. If confirmed malicious, this could allow attackers to maintain persistence and hinder incident response efforts.

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

Data Source

Name Platform Sourcetype Source
CrowdStrike ProcessRollup2 N/A 'crowdstrike:events:sensor' 'crowdstrike'
Sysmon EventID 1 Windows icon Windows 'xmlwineventlog' 'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'
Windows Event Log Security 4688 Windows icon Windows 'xmlwineventlog' 'XmlWinEventLog:Security'

Macros Used

Name Value
security_content_ctime convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)
icacls_deny_command_filter search *
icacls_deny_command_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK
+ Kill Chain Phases
+ NIST
+ CIS
- Threat Actors
ID Technique Tactic
T1222 File and Directory Permissions Modification Defense Evasion
Exploitation
DE.AE
CIS 10

Default Configuration

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

Setting Value
Disabled true
Cron Schedule 0 * * * *
Earliest Time -70m@m
Latest Time -10m@m
Schedule Window auto
Creates Risk Event True
This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.

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

Unknown. It is possible some administrative scripts use ICacls. Filter as needed.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

Process name $process_name$ with deny argument executed by $user$ to change security permission of a specific file or directory on host $dest$

Risk Object Risk Object Type Risk Score Threat Objects
user user 72 No Threat Objects
dest system 72 No Threat Objects

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset XmlWinEventLog:Microsoft-Windows-Sysmon/Operational XmlWinEventLog
Integration ✅ Passing Dataset XmlWinEventLog:Microsoft-Windows-Sysmon/Operational XmlWinEventLog

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: 9