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Description

Monitor for changes of the ExecutionPolicy in the registry to the values "unrestricted" or "bypass," which allows the execution of malicious scripts.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2023-04-14
  • Author: Steven Dick, Patrick Bareiss, Splunk
  • ID: c2590137-0b08-4985-9ec5-6ae23d92f63d

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1059 Command and Scripting Interpreter Execution
T1059.001 PowerShell Execution
Kill Chain Phase
  • Installation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


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| tstats `security_content_summariesonly` count min(_time) AS firstTime max(_time) AS lastTime FROM datamodel=Endpoint.Processes BY _time span=1h Processes.user Processes.process_id Processes.process_name Processes.process Processes.process_path Processes.dest Processes.parent_process_name Processes.parent_process Processes.process_guid 
| `drop_dm_object_name(Processes)` 
| join process_guid [ 
| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Registry WHERE (Registry.registry_path=*Software\\Microsoft\\Powershell\\1\\ShellIds\\Microsoft.PowerShell* Registry.registry_value_name=ExecutionPolicy (Registry.registry_value_data=Unrestricted OR Registry.registry_value_data=Bypass)) BY _time span=1h Registry.registry_path Registry.registry_key_name Registry.registry_value_name Registry.registry_value_data Registry.process_guid 
| `drop_dm_object_name(Registry)`] 
| fields firstTime lastTime dest user parent_process_name parent_process process_name process_path process registry_key_name registry_path registry_value_name registry_value_data process_guid 
| where isnotnull(registry_value_data) 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `set_default_powershell_execution_policy_to_unrestricted_or_bypass_filter`

Macros

The SPL above uses the following Macros:

:information_source: set_default_powershell_execution_policy_to_unrestricted_or_bypass_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
  • Processes.user
  • Processes.dest
  • Processes.process_id
  • Processes.process_name
  • Processes.process
  • Processes.process_path
  • Processes.parent_process_name
  • Processes.parent_process
  • Processes.process_guid
  • Registry.dest
  • Registry.registry_value_name
  • Registry.registry_key_name
  • Registry.registry_path
  • Registry.registry_value_data
  • Registry.process_guid

How To Implement

To successfully implement this search, you need to be ingesting logs with the registry value name, registry path, and registry value data from your endpoints. If you are using Sysmon, you must have at least version 2.0 of the offical Sysmon TA. https://splunkbase.splunk.com/app/5709

Known False Positives

Administrators may attempt to change the default execution policy on a system for a variety of reasons. However, setting the policy to "unrestricted" or "bypass" as this search is designed to identify, would be unusual. Hits should be reviewed and investigated as appropriate.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
48.0 60 80 A registry modification in $registry_path$ with reg key $registry_key_name$ and reg value $registry_value_name$ in host $dest$

: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: 8