splunk_escuHunting

GetNetTcpconnection with PowerShell Script Block

The following analytic detects the execution of the `Get-NetTcpconnection` PowerShell cmdlet using PowerShell Script Block Logging (EventCode=4104). This cmdlet lists network connections on a system, which adversaries may use for situational awareness and Active Directory discovery. Monitoring this activity is crucial as it can indicate reconnaissance efforts by an attacker. If confirmed malicious, this behavior could allow an attacker to map the network, identify critical systems, and plan further attacks, potentially leading to data exfiltration or lateral movement within the network.

Detection Query

`powershell` EventCode=4104 (ScriptBlockText = "*Get-NetTcpconnection*")
  | fillnull
  | stats count min(_time) as firstTime max(_time) as lastTime
    BY dest signature signature_id
       user_id vendor_product EventID
       Guid Opcode Name
       Path ProcessID ScriptBlockId
       ScriptBlockText
  | `security_content_ctime(firstTime)`
  | `security_content_ctime(lastTime)`
  | `getnettcpconnection_with_powershell_script_block_filter`

Author

Mauricio Velazco, Splunk

Data Sources

Powershell Script Block Logging 4104

References

Raw Content

name: GetNetTcpconnection with PowerShell Script Block
id: 091712ff-b02a-4d43-82ed-34765515d95d
version: 10
creation_date: '2021-08-24'
modification_date: '2026-05-13'
author: Mauricio Velazco, Splunk
status: production
type: Hunting
description: The following analytic detects the execution of the `Get-NetTcpconnection` PowerShell cmdlet using PowerShell Script Block Logging (EventCode=4104). This cmdlet lists network connections on a system, which adversaries may use for situational awareness and Active Directory discovery. Monitoring this activity is crucial as it can indicate reconnaissance efforts by an attacker. If confirmed malicious, this behavior could allow an attacker to map the network, identify critical systems, and plan further attacks, potentially leading to data exfiltration or lateral movement within the network.
data_source:
    - Powershell Script Block Logging 4104
search: |-
    `powershell` EventCode=4104 (ScriptBlockText = "*Get-NetTcpconnection*")
      | fillnull
      | stats count min(_time) as firstTime max(_time) as lastTime
        BY dest signature signature_id
           user_id vendor_product EventID
           Guid Opcode Name
           Path ProcessID ScriptBlockId
           ScriptBlockText
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `getnettcpconnection_with_powershell_script_block_filter`
how_to_implement: To successfully implement this analytic, you will need to enable PowerShell Script Block Logging on some or all endpoints. Additional setup here https://help.splunk.com/en/security-offerings/splunk-user-behavior-analytics/get-data-in/5.4.1/add-other-data-to-splunk-uba/configure-powershell-logging-to-see-powershell-anomalies-in-splunk-uba.
known_false_positives: Administrators or power users may use this PowerShell commandlet for troubleshooting.
references:
    - https://attack.mitre.org/techniques/T1049/
    - https://docs.microsoft.com/en-us/powershell/module/nettcpip/get-nettcpconnection?view=windowsserver2019-ps
analytic_story:
    - Active Directory Discovery
asset_type: Endpoint
mitre_attack_id:
    - T1049
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/powershell_script_block_logging/nettcpconnection.log
          source: XmlWinEventLog:Microsoft-Windows-PowerShell/Operational
          sourcetype: XmlWinEventLog
      test_type: unit