Detection: GetNetTcpconnection with PowerShell Script Block

Updated Date: 2024-10-17 ID: 091712ff-b02a-4d43-82ed-34765515d95d Author: Mauricio Velazco, Splunk Type: Hunting Product: Splunk Enterprise Security

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.

Search

1`powershell` EventCode=4104 (ScriptBlockText = "*Get-NetTcpconnection*") 
2| stats count min(_time) as firstTime max(_time) as lastTime by Opcode Computer UserID EventCode ScriptBlockText 
3| `security_content_ctime(firstTime)` 
4| `getnettcpconnection_with_powershell_script_block_filter`

Data Source

Name	Platform	Sourcetype	Source
Powershell Script Block Logging 4104	Windows	`'xmlwineventlog'`	`'XmlWinEventLog:Microsoft-Windows-PowerShell/Operational'`

Macros Used

Name	Value
powershell	`(source=WinEventLog:Microsoft-Windows-PowerShell/Operational OR source="XmlWinEventLog:Microsoft-Windows-PowerShell/Operational")`
getnettcpconnection_with_powershell_script_block_filter	`search *`

getnettcpconnection_with_powershell_script_block_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1049	System Network Connections Discovery	Discovery

KillChainPhase.EXPLOITAITON

NistCategory.DE_AE

Cis18Value.CIS_10

APT1

APT3

APT32

APT38

APT41

APT5

Andariel

BackdoorDiplomacy

Chimera

Earth Lusca

FIN13

GALLIUM

HEXANE

INC Ransom

Ke3chang

Lazarus Group

Magic Hound

MuddyWater

Mustang Panda

OilRig

Poseidon Group

Sandworm Team

TeamTNT

Threat Group-3390

ToddyCat

Tropic Trooper

Turla

Volt Typhoon

admin@338

menuPass

Default Configuration

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

Setting	Value
Disabled	true
Cron Schedule	`0 * * * *`
Earliest Time	`-70m@m`
Latest Time	`-10m@m`
Schedule Window	`auto`
Creates Risk Event	False

This configuration file applies to all detections of type hunting.

Implementation

To successfully implement this analytic, you will need to enable PowerShell Script Block Logging on some or all endpoints. Additional setup here https://docs.splunk.com/Documentation/UBA/5.0.4.1/GetDataIn/AddPowerShell#Configure_module_logging_for_PowerShell.

Known False Positives

Administrators or power users may use this PowerShell commandlet for troubleshooting.

Associated Analytic Story

Active Directory Discovery

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
Network Connection discovery on $Computer$ by $user$	15	30	50

The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-PowerShell/Operational`	`XmlWinEventLog`
Integration	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-PowerShell/Operational`	`XmlWinEventLog`

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: 4