Detection: GetNetTcpconnection with PowerShell

Description

The following analytic identifies the execution of powershell.exe with the Get-NetTcpConnection command, which lists current TCP connections on a system. This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on process names and command-line executions. Monitoring this activity is significant as it may indicate an adversary or Red Team performing network reconnaissance or situational awareness. If confirmed malicious, this activity could allow attackers to map network connections, aiding in lateral movement or further exploitation within the network.

Search

1
2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where (Processes.process_name="powershell.exe") (Processes.process=*Get-NetTcpConnection*) by Processes.dest Processes.user Processes.parent_process Processes.process_name Processes.process Processes.process_id Processes.parent_process_id 
3| `drop_dm_object_name(Processes)` 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `getnettcpconnection_with_powershell_filter`

Data Source

Name	Platform	Sourcetype	Source
CrowdStrike ProcessRollup2	N/A	'crowdstrike:events:sensor'	'crowdstrike'
Sysmon EventID 1	Windows	'xmlwineventlog'	'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'
Windows Event Log Security 4688	Windows	'xmlwineventlog'	'XmlWinEventLog:Security'

Macros Used

Annotations

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Implementation

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

Administrators or power users may use this command for troubleshooting.

Associated Analytic Story

• Active Directory Discovery

Risk Based Analytics (RBA)

References

• https://attack.mitre.org/techniques/T1049/

• https://docs.microsoft.com/en-us/powershell/module/nettcpip/get-nettcpconnection?view=windowsserver2019-ps

Detection Testing

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: GitHub | Version: 3