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Description

The following hunting analytic identifies PowerShell commands utilizing the WindowStyle parameter to hide the window on the compromised endpoint. This combination of command-line options is suspicious because it is overriding the default PowerShell execution policy, attempts to hide its activity from the user, and connects to the Internet. Removed in this version of the query is New-Object. The analytic identifies all variations of WindowStyle, as PowerShell allows the ability to shorten the parameter. For example w, win, windowsty and so forth. In addition, through our research it was identified that PowerShell will interpret different command switch types beyond the hyphen. We have added endash, emdash, horizontal bar, and forward slash.

  • Type: Hunting
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2021-10-05
  • Author: David Dorsey, Michael Haag Splunk
  • ID: ee18ed37-0802-4268-9435-b3b91aaa18db

ATT&CK

ID Technique Tactic
T1059.001 PowerShell Execution

| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where `process_powershell` by Processes.user Processes.process_name Processes.process Processes.parent_process_name Processes.original_file_name Processes.dest Processes.process_id 
| `drop_dm_object_name(Processes)` 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| where match(process,"(?i)[\-
|\/
|–
|—
|―]w(in*d*o*w*s*t*y*l*e*)*\s+[^-]") 
| `malicious_powershell_process___connect_to_internet_with_hidden_window_filter`

Associated Analytic Story

How To Implement

You must be ingesting data that records process activity from your hosts to populate the Endpoint data model in the Processes node. You must also be ingesting logs with both the process name and command line from your endpoints. The command-line arguments are mapped to the "process" field in the Endpoint data model.

Required field

  • _time
  • Processes.process
  • Processes.process_name
  • Processes.user
  • Processes.parent_process_name
  • Processes.dest

Kill Chain Phase

  • Command and Control
  • Actions on Objectives

Known False Positives

Legitimate process can have this combination of command-line options, but it's not common.

RBA

Risk Score Impact Confidence Message
81.0 90 90 PowerShell processes $process$ started with parameters to modify the execution policy of the run, run in a hidden window, and connect to the Internet on host $dest$ executed by user $user$.

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