Detection rules › Splunk
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 coverage
| Tactic | Techniques |
|---|---|
| Execution | T1059.001 Command and Scripting Interpreter: PowerShell |
Event coverage
| Provider | Event | Title |
|---|---|---|
| Sysmon | Event ID 1 | Process creation |
| Security-Auditing | Event ID 4688 | A new process has been created. |
Rule body splunk
name: PowerShell - Connect To Internet With Hidden Window
id: ee18ed37-0802-4268-9435-b3b91aaa18db
version: 16
creation_date: '2020-04-29'
modification_date: '2026-05-13'
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/
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
category: endpoint
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
test_type: unit
Stages and Predicates
Stage 1: tstats
| 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
Stage 2: search
| `drop_dm_object_name(Processes)`
Stage 3: search
| `security_content_ctime(firstTime)`
Stage 4: search
| `security_content_ctime(lastTime)`
Stage 5: where
| where match(process,"(?i)[\-
| \/
| –
| —
| ―]w(in*d*o*w*s*t*y*l*e*)*\s+[^-]")
Stage 6: search
| `powershell___connect_to_internet_with_hidden_window_filter`
Indicators
Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.
| Field | Kind | Values |
|---|---|---|
Processes.original_file_name | eq |
|
Processes.process_name | eq |
|
process | match |
|