Detection: Powershell Remote Services Add TrustedHost

Updated Date: 2024-05-20 ID: bef21d24-297e-45e3-9b9a-c6ac45450474 Author: Teoderick Contreras, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects the execution of a PowerShell script that modifies the 'TrustedHosts' configuration via EventCode 4104. It leverages PowerShell Script Block Logging to identify commands targeting WSMan settings, specifically those altering or concatenating trusted hosts. This activity is significant as it can indicate attempts to manipulate remote connection settings, potentially allowing unauthorized remote access. If confirmed malicious, this could enable attackers to establish persistent remote connections, bypass security protocols, and gain unauthorized access to sensitive systems and data.

1`powershell` EventCode=4104  ScriptBlockText = "*WSMan:\\localhost\\Client\\TrustedHosts*" ScriptBlockText IN ("* -Value *", "* -Concatenate *") 
2| rename Computer as dest, UserID as user 
3| stats count min(_time) as firstTime max(_time) as lastTime by EventCode ScriptBlockText dest user 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `powershell_remote_services_add_trustedhost_filter`

Data Source

Name Platform Sourcetype Source Supported App
Powershell Script Block Logging 4104 Windows icon Windows 'xmlwineventlog' 'XmlWinEventLog:Microsoft-Windows-PowerShell/Operational' N/A

Macros Used

Name Value
powershell (source=WinEventLog:Microsoft-Windows-PowerShell/Operational OR source="XmlWinEventLog:Microsoft-Windows-PowerShell/Operational")
powershell_remote_services_add_trustedhost_filter search *
powershell_remote_services_add_trustedhost_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
T1021.006 Windows Remote Management Lateral Movement
T1021 Remote Services Lateral Movement
KillChainPhase.EXPLOITAITON
NistCategory.DE_CM
Cis18Value.CIS_10
Chimera
FIN13
Threat Group-3390
Wizard Spider
Wizard Spider

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 Notable Yes
Rule Title %name%
Rule Description %description%
Notable Event Fields user, dest
Creates Risk Event True
This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

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

user and network administrator may used this function to add trusted host.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
a powershell script adding a remote trustedhost on $dest$ . 64 80 80
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: 2