splunk_escuHunting

PowerShell - Connect To Internet With Hidden Window

The following analytic detects PowerShell commands using the WindowStyle parameter to hide the window while connecting to the Internet. This behavior is identified through Endpoint Detection and Response (EDR) telemetry, focusing on command-line executions that include variations of the WindowStyle parameter. This activity is significant because it attempts to bypass default PowerShell execution policies and conceal its actions, which is often indicative of malicious intent. If confirmed malicious, this could allow an attacker to execute commands stealthily, potentially leading to unauthorized data exfiltration or further compromise of the endpoint.

MITRE ATT&CK

T1059.001

execution

Detection Query

| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Processes
  WHERE `process_powershell`
  BY Processes.action Processes.dest Processes.original_file_name
     Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid
     Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path
     Processes.process Processes.process_exec Processes.process_guid
     Processes.process_hash Processes.process_id Processes.process_integrity_level
     Processes.process_name Processes.process_path Processes.user
     Processes.user_id Processes.vendor_product
| `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`

Author

David Dorsey, Michael Haag Splunk

Created

2026-02-25

Data Sources

Sysmon EventID 1Windows Event Log Security 4688CrowdStrike ProcessRollup2

References

Tags

AgentTeslaHAFNIUM GroupHermetic WiperPossible Backdoor Activity Associated With MUDCARP Espionage CampaignsMalicious PowerShellData DestructionLog4Shell CVE-2021-44228

Raw Content

name: PowerShell - Connect To Internet With Hidden Window
id: ee18ed37-0802-4268-9435-b3b91aaa18db
version: 15
date: '2026-02-25'
author: David Dorsey, Michael Haag Splunk
status: production
type: Hunting
description: The following analytic detects PowerShell commands using the WindowStyle parameter to hide the window while connecting to the Internet. This behavior is identified through Endpoint Detection and Response (EDR) telemetry, focusing on command-line executions that include variations of the WindowStyle parameter. This activity is significant because it attempts to bypass default PowerShell execution policies and conceal its actions, which is often indicative of malicious intent. If confirmed malicious, this could allow an attacker to execute commands stealthily, potentially leading to unauthorized data exfiltration or further compromise of the endpoint.
data_source:
    - Sysmon EventID 1
    - Windows Event Log Security 4688
    - CrowdStrike ProcessRollup2
search: |-
    | tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Processes
      WHERE `process_powershell`
      BY Processes.action Processes.dest Processes.original_file_name
         Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid
         Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path
         Processes.process Processes.process_exec Processes.process_guid
         Processes.process_hash Processes.process_id Processes.process_integrity_level
         Processes.process_name Processes.process_path Processes.user
         Processes.user_id Processes.vendor_product
    | `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`
how_to_implement: The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the `Processes` node of the `Endpoint` data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.
known_false_positives: Legitimate process can have this combination of command-line options, but it's not common.
references:
    - https://regexr.com/663rr
    - https://github.com/redcanaryco/AtomicTestHarnesses/blob/master/Windows/TestHarnesses/T1059.001_PowerShell/OutPowerShellCommandLineParameter.ps1
    - https://ss64.com/ps/powershell.html
    - https://twitter.com/M_haggis/status/1440758396534214658?s=20
    - https://blog.netlab.360.com/ten-families-of-malicious-samples-are-spreading-using-the-log4j2-vulnerability-now/
tags:
    analytic_story:
        - AgentTesla
        - HAFNIUM Group
        - Hermetic Wiper
        - Possible Backdoor Activity Associated With MUDCARP Espionage Campaigns
        - Malicious PowerShell
        - Data Destruction
        - Log4Shell CVE-2021-44228
    asset_type: Endpoint
    cve:
        - CVE-2021-44228
    mitre_attack_id:
        - T1059.001
    product:
        - Splunk Enterprise
        - Splunk Enterprise Security
        - Splunk Cloud
    security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1059.001/hidden_powershell/windows-sysmon.log
          source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
          sourcetype: XmlWinEventLog