T1546.007 Netsh Helper DLL

> Sub-technique of: T1546

High-Level Description

Adversaries may establish persistence by executing malicious content triggered by Netsh Helper DLLs. Netsh.exe (also referred to as Netshell) is a command-line scripting utility used to interact with the network configuration of a system. It contains functionality to add helper DLLs for extending functionality of the utility. The paths to registered netsh.exe helper DLLs are entered into the Windows Registry at <code>HKLM\SOFTWARE\Microsoft\Netsh</code>.

Adversaries can use netsh.exe helper DLLs to trigger execution of arbitrary code in a persistent manner. This execution would take place anytime netsh.exe is executed, which could happen automatically, with another persistence technique, or if other software (ex: VPN) is present on the system that executes netsh.exe as part of its normal functionality.

Kill Chain Phase

• Privilege Escalation (TA0004)
• Persistence (TA0003)

Platforms: Windows

What to Check

• ] Identify if Netsh Helper DLL technique is applicable to target environment
• ] Check Windows systems for indicators of Netsh Helper DLL
• ] Assess detection coverage (1 detection strategies)

How to Test

Atomic Red Team Tests

The following tests are from Atomic Red Team and provide actionable ways to test this technique:

Atomic Test 1: Netsh Helper DLL Registration

You can register a "helper dll" with Netsh as a persistance mechanism. The code in the dll is executed every time netsh.exe is called. The NetshHelper.dll provided with the atomic will simply launch notepad when netsh.exe is run.

Blog Sample DLL code

Supported Platforms: windows Elevation Required: Yes

cmd
netsh.exe add helper "#{helper_file}"
taskkill /im notepad.exe /t /f > NUL 2>&1

Dependencies:

• Helper DLL must exist on disk at specified location (#{helper_file})

Manual Testing

If Atomic Red Team tests are not applicable, manually verify the technique by:

1. Identify Attack Surface: Determine if the target environment is susceptible to Netsh Helper DLL by examining the target platforms (Windows).

1. Assess Existing Defenses: Review whether mitigations for T1546.007 are in place. If defenses are absent or misconfigured, this technique may be exploitable.

1. Execute Test: Use tools and methods described in the MITRE ATT&CK page and external references below.

Remediation Guide

No specific mitigations documented for this technique.

Detection

Detection Strategy for Netsh Helper DLL Persistence via Registry and Child Process Monitoring (Windows)

Risk Assessment

| Finding | Severity | Impact | | ------------------------------------- | -------- | -------------------- | | Netsh Helper DLL technique applicable | Low | Privilege Escalation |

CWE Categories

| CWE ID | Title | | ------- | ----------------------------- | | CWE-269 | Improper Privilege Management |

References

• Demaske Netsh Persistence
• TechNet Netsh
• Github Netsh Helper CS Beacon
• Atomic Red Team - T1546.007
• MITRE ATT&CK - T1546.007