Netsh Helper DLL

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. [1] The paths to registered netsh.exe helper DLLs are entered into the Windows Registry at HKLM\SOFTWARE\Microsoft\Netsh.

Adversaries can use netsh.exe with helper DLLs to proxy execution of arbitrary code in a persistent manner when netsh.exe is executed automatically with another Persistence technique or if other persistent software is present on the system that executes netsh.exe as part of its normal functionality. Examples include some VPN software that invoke netsh.exe. [2]

Proof of concept code exists to load Cobalt Strike's payload using netsh.exe helper DLLs. [3]

ID: T1128

Tactic: Persistence

Platform:  Windows

System Requirements:  [netsh](https://attack.mitre.org/software/S0108)

Permissions Required:  Administrator, SYSTEM

Data Sources:  DLL monitoring, Windows Registry, Process monitoring

Contributors:  Matthew Demaske, Adaptforward
Version: 1.0

Mitigations

This type of attack technique cannot be easily mitigated with preventive controls since it is based on the abuse of system features.

Examples

Name Description
netsh

netsh can be used as a persistence proxy technique to execute a helper DLL when netsh.exe is executed.[2]

Detection

It is likely unusual for netsh.exe to have any child processes in most environments. Monitor process executions and investigate any child processes spawned by netsh.exe for malicious behavior. Monitor the HKLM\SOFTWARE\Microsoft\Netsh registry key for any new or suspicious entries that do not correlate with known system files or benign software. [2]

References