Cyber security

AMSI Bypass via VEH – Technique Using Vectored Exception Handling

A PowerShell AMSI Bypass technique via Vectored Exception Handler (VEH). This technique does not perform assembly instruction patching, function hooking or Import Address Table (IAT) modification.


How It Works:

For this technique to work, you must first inject the VEH DLL into the PowerShell process. This can be done either by injecting the DLL or via DLL hijacking .

This technique works by setting up a hardware breakpoint on the function AmsiScanBuffer on all PowerShell process threads, then installing a VEH to handle the trigger of this breakpoint.

When a thread calls AmsiScanBuffer, the VEH will make the thread to exit the function without executing anything and setting the result of the function to AMSI_RESULT_CLEAN.

This is all done inside the VEH, without modifying the code of the process or without any PE modifications.


Usage:

For demonstration purposes, this repository contains a very basic DLL injector. Use it this way:

  • 1.) Compile the DLL Injector and VEH DLL.
  • 2.) Open an instance of PowerShell.
  • 3.) Run the DLL injector by providing the FULL PATH to the DLL. Example:
./DLL_Injector.exe C:\Windows\Temp\AMSI_VEH.DLL
Varshini

Varshini is a Cyber Security expert in Threat Analysis, Vulnerability Assessment, and Research. Passionate about staying ahead of emerging Threats and Technologies.

Recent Posts

How to Install Docker on Ubuntu (Step-by-Step Guide)

Docker is a powerful open-source containerization platform that allows developers to build, test, and deploy…

14 hours ago

Uninstall Docker on Ubuntu

Docker is one of the most widely used containerization platforms. But there may come a…

14 hours ago

Admin Panel Dorks : A Complete List of Google Dorks

Introduction Google Dorking is a technique where advanced search operators are used to uncover information…

2 days ago

Log Analysis Fundamentals

Introduction In cybersecurity and IT operations, logging fundamentals form the backbone of monitoring, forensics, and…

3 days ago

Networking Devices 101: Understanding Routers, Switches, Hubs, and More

What is Networking? Networking brings together devices like computers, servers, routers, and switches so they…

3 days ago

Sock Puppets in OSINT: How to Build and Use Research Accounts

Introduction In the world of Open Source Intelligence (OSINT), anonymity and operational security (OPSEC) are…

3 days ago