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Description

The following analytic identifies the use of cacls.exe, icacls.exe or xcacls.exe placing the grant permission on a file or directory. Adversaries perform this behavior to allow components of their files to run, however it allows responders to review or gaining access to adversary files on disk.

  • Type: TTP
  • Product: Splunk Behavioral Analytics
  • Datamodel: Endpoint_Processes
  • Last Updated: 2021-11-30
  • Author: Teoderick Contreras, Splunk
  • ID: c6da561a-cd29-11eb-ae65-acde48001122

ATT&CK

ID Technique Tactic
T1222 File and Directory Permissions Modification Defense Evasion
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| from read_ssa_enriched_events() 
| eval timestamp=parse_long(ucast(map_get(input_event, "_time"), "string", null)), cmd_line=ucast(map_get(input_event, "process"), "string", null), process_name=ucast(map_get(input_event, "process_name"), "string", null), process_path=ucast(map_get(input_event, "process_path"), "string", null), parent_process_name=ucast(map_get(input_event, "parent_process_name"), "string", null), event_id=ucast(map_get(input_event, "event_id"), "string", null) 
| where cmd_line IS NOT NULL AND match_regex(cmd_line, /(?i)grant/)=true AND (process_name="cacls.exe" OR process_name="xcacls.exe" OR process_name="icacls.exe") 
| eval start_time=timestamp, end_time=timestamp, entities=mvappend(ucast(map_get(input_event, "dest_user_id"), "string", null), ucast(map_get(input_event, "dest_device_id"), "string", null)), body=create_map(["event_id", event_id, "cmd_line", cmd_line, "process_name", process_name, "parent_process_name", parent_process_name, "process_path", process_path]) 
| into write_ssa_detected_events();

Macros

The SPL above uses the following Macros:

Note that grant_permission_using_cacls_utility_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required field

  • _time
  • dest_device_id
  • process_name
  • parent_process_name
  • process_path
  • dest_user_id
  • process
  • cmd_line

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 icacls.exe may be used.

Known False Positives

System administrators may use cacls utilities but this is not a common practice. Filter as needed.

Associated Analytic story

Kill Chain Phase

  • Exploitation

RBA

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

Note that risk score is calculated base on the following formula: (Impact * Confidence)/100

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

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