Deny Permission using Cacls Utility
Description
The following analytic identifies the use of cacls.exe
, icacls.exe
or xcacls.exe
placing the deny permission on a file or directory. Adversaries perform this behavior to prevent responders from reviewing or gaining access to adversary files on disk.
- Type: TTP
- Product: Splunk Behavioral Analytics
- Datamodel: Endpoint_Processes
- Last Updated: 2021-11-29
- Author: Teoderick Contreras, Splunk
- ID: b76eae28-cd25-11eb-9c92-acde48001122
Annotations
Kill Chain Phase
- Exploitation
NIST
- PR.AC
- PR.IP
CIS20
- CIS 14
- CIS 16
CVE
Search
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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)deny/)=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:
deny_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 fields
List of fields required to use this analytic.
- _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
RBA
Risk Score | Impact | Confidence | Message |
---|---|---|---|
35.0 | 50 | 70 | A cacls process $process_name$ with commandline $cmd_line$ try to deny a permission of a file or directory in host $dest_device_id$ |
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: 3