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Description

This analytic identifies suspicious modification of ACL permission to a files or folder to make it available to everyone or to a specific user. This technique may be used by the adversary to evade ACLs or protected files access. This changes is commonly configured by the file or directory owner with appropriate permission. This behavior raises suspicion if this command is seen on an endpoint utilized by an account with no permission to do so.

  • Type: Anomaly

  • Product: Splunk Behavioral Analytics

  • Last Updated: 2022-03-17
  • Author: Teoderick Contreras, Splunk
  • ID: 9ae9a48a-cdbe-11eb-875a-acde48001122

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1222 File and Directory Permissions Modification Defense Evasion
Kill Chain Phase
  • Exploitation
NIST
  • DE.AE
CIS20
  • CIS 10
CVE 


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 $main = from source  
| eval timestamp = time  
| eval metadata_uid = metadata.uid  
| eval process_pid = process.pid 
| eval process_file = process.file 
| eval process_file_path = process_file.path 
| eval process_file_name = lower(process_file.name) 
| eval process_cmd_line = process.cmd_line 
| eval actor_user = actor.user 
| eval actor_user_name = actor_user.name 
| eval actor_process = actor.process 
| eval actor_process_pid = actor_process.pid 
| eval actor_process_file = actor_process.file 
| eval actor_process_file_path = actor_process_file.path 
| eval actor_process_file_name = actor_process_file.name 
| eval device_hostname = device.hostname 
| where (match(process_cmd_line, /(?i)S-1-1-0:/)=true OR match(process_cmd_line, /(?i)SYSTEM:/)=true OR match(process_cmd_line, /(?i)everyone:/)=true) AND (process_file_name IN ("icacls.exe", "xcacls.exe", "cacls.exe")) --finding_report--

Macros

The SPL above uses the following Macros:

:information_source: modify_acls_permission_of_files_or_folders_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • process.pid
  • process.file.path
  • process.file.name
  • process.cmd_line
  • actor.user.name
  • actor.process.pid
  • actor.process.file.path
  • actor.process.file.name
  • device.hostname

How To Implement

To successfully implement this search, you need to be ingesting logs with the process name, parent process, and command-line executions from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA. Tune and filter known instances where renamed cacls.exe may be used.

Known False Positives

System administrators may use this windows utility. filter is needed.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
35.0 50 70 A cacls process $process_name$ with commandline $process$ try to modify a permission of a file or directory in host $dest_device_id$

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

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 | version: 7