PowerShell - Connect To Internet With Hidden Window

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: 2023-04-14
Author: David Dorsey, Michael Haag Splunk
ID: ee18ed37-0802-4268-9435-b3b91aaa18db

Annotations

ATT&CK

ID	Technique	Tactic
T1059.001	PowerShell	Execution

T1059

Command and Scripting Interpreter

Execution

Kill Chain Phase

Installation

NIST

DE.AE

CIS20

CIS 10

CVE

ID	Summary	CVSS
CVE-2021-44228	Apache Log4j2 2.0-beta9 through 2.15.0 (excluding security releases 2.12.2, 2.12.3, and 2.3.1) JNDI features used in configuration, log messages, and parameters do not protect against attacker controlled LDAP and other JNDI related endpoints. An attacker who can control log messages or log message parameters can execute arbitrary code loaded from LDAP servers when message lookup substitution is enabled. From log4j 2.15.0, this behavior has been disabled by default. From version 2.16.0 (along with 2.12.2, 2.12.3, and 2.3.1), this functionality has been completely removed. Note that this vulnerability is specific to log4j-core and does not affect log4net, log4cxx, or other Apache Logging Services projects.	9.3

Search

| 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+[^-]") 
| `powershell___connect_to_internet_with_hidden_window_filter`

Macros

The SPL above uses the following Macros:

powershell_-_connect_to_internet_with_hidden_window_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.process
Processes.process_name
Processes.user
Processes.parent_process_name
Processes.dest

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.

Known False Positives

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

Associated Analytic Story

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 $user$.

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

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