A Review of the Sektor7 RED TEAM Operator: Malware Development Essentials Course

Introduction

I recently discovered the Sektor7 RED TEAM Operator: Malware Development Essentials course on 0x00sec and it instantly grabbed my interest. Lately I’ve been working on improving my programming skills, especially in C, on Windows, and in the context of red teaming. This course checked all those boxes, and was on sale for $95 to boot. So I broke out the credit card and purchased the course.

Custom code can be a huge benefit during pentesting and red team operations, and I’ve been trying to level up in that area. I’m a pentester by trade, with a little red teaming thrown in, so this course was right in my wheelhouse. My C is slightly rusty, not having done much with it since college, and almost exclusively on Linux rather than Windows. I wasn’t sure how prepared I would be for the course, but I was willing to try harder and do as much research as I needed to get through it.

Course Overview

The course description reads like this:

It will teach you how to develop your own custom malware for latest Microsoft Windows 10. And by custom malware we mean building a dropper for any payload you want (Metasploit meterpreter, Empire or Cobalt Strike beacons, etc.), injecting your shellcodes into remote processes, creating trojan horses (backdooring existing software) and bypassing Windows Defender AV.

It’s aimed at pentesters, red teamers, and blue teamers wanting to learn the details of offensive malware. It covers a range of topics aimed at developing and delivering a payload via a dropper file, using a variety of mechanisms to encrypt, encode, or obfuscate different elements of the executable. From the course page the topics include:

What is malware development

What is PE file structure

file structure Where to store your payload inside PE

How to encode and encrypt payloads

How and why obfuscate function calls

How to backdoor programs

How to inject your code into remote processes

RTO: Malware Development Essentials covers the above with 9 different modules, starting with the basics of the PE file structure, ending with combining all the techniques taught to create a dropper executable that evades Windows Defender while injecting a shellcode payload into another process.

The course is delivered via a content platform called Podia, which allows streaming of the course videos and access to code samples and the included pre-configured Windows virtual machine for compiling and testing code. Podia worked quite well, and the provided code was clear, comprehensive, well-commented, and designed to be reusable later to create your own executables.

Module 1: Intro and Setup

The intro and setup module covers a quick into to the course and getting access to the excellent sample code and a virtual machine OVA image that contains a development environment, debugger, and tools like PEBear. I really like that the VM was provided, as it made jumping in and following along effortless, as well as saving time creating a development environment.

Module 2: Portable Executable

This module covers the Portable Executable (PE) format, how it is structured, and where things like code and data reside within it. It introduces PEBear, a tool for exploring PE files I’d not used before. It also covers the differences between executables and DLLs on Windows.

Module 3: Droppers

The dropper module covers how and where to store payload shellcode within a PE, using the .text, .data, and .rsrc sections. It also covers including external resources and compiling them into the final .exe.

Module 4: Obfuscation and Hiding

Obfuscation and hiding was one of my favorite modules. Anyone that has had their shellcode or implants caught will appreciate knowing how to use AES and XOR to encrypt payloads, and how to dynamically decrypt them at runtime to prevent static analysis. I also learned a lot about Windows and the Windows API through the sections on dynamically resolving functions and function call obfuscation.

Module 5: Backdoors and Trojans

This section covered code caves, hiding data within a PE, and how to backdoor an existing executable with a payload. x64dbg debugger is used extensively to examine a binary, find space for a payload, and ensure that the existing binary still functions normally. Already knowing assembly helped me here, but it’s explained well enough for those with little to no assembly knowledge to follow along.

Module 6: Code Injection

I learned a ton from this section, and it really clarified my knowledge of process injection, including within a process, between processes, and using a DLL. VirtualAllocEx , WriteProcessMemory , and CreateRemoteThread are more than just some function names involving process injection to me now.

Module 7: Extras

This module covered the differences between GUI and console programs on Windows, and how to ensure the dreaded black console window does not appear when your payload is executed.

Module 8: Combined Project

This was the culmination of the course, where you are walked through combining all the individual techniques and tools you learned throughout the course into a single executable. I suggest watching it and then doing it yourself independently to really internalize the material.

Module 9: Assignment

The last module is an assignment, which asks you to take what you’ve learned in the combined project and more fully implement some of the techniques, as well as providing some suggestions for real-world applications of the course content you can try by yourself.

Takeaways

I learned a heck of a lot from this course. It was not particularly long, but it covered the topics thoroughly and gave me a good base to build from. I can’t remember a course where I learned so much in so little time. Not only did I learn what was intended by the course, but there were a lot of ancillary things I picked up along the way that weren’t explicitly covered.

C on Windows

I found the course to be a good introduction to C on Windows, assuming you are already familiar with C. It’s not a beginning C programming course by any means. Most of my experience with C has been on Linux with gcc , and the course provided practical examples of how to write C on Windows, how to use MSDN effectively, how to structure programs, and how to interact with DLLs. I was familiar with many of the topics at a high level, but there’s no substitute for digging in and writing code.

Intro to the Windows API

I also learned a great deal on how the Windows API works and how to interact with it. The section on resolving functions manually was especially good. I have a much stronger grasp of how Windows presents different functionalities, and how to lookup functions and APIs on MSDN to incorporate them into my own code.

Making Windows Concepts Concrete

As mentioned above, there were a lot of areas I knew about at a high level, like process injection, DLLs, the Import Address Table, even some Windows APIs like WriteProcessMemory and CreateRemoteThread . But once I looked up their function signatures on MSDN, called them myself, created my own DLLs, and obfuscated the IAT, I had a much more concrete understanding of each topic, and I feel much more prepared to write my own tools in the future using what I’ve learned.

A Framework For Building Your Own Payloads

The way the course built from small functions and examples, all meant to be reused and built upon, really made the course worthwhile and feel like an investment I could take advantage of later in my own tools. I’ve already managed to craft a dropper that executes a staged Cobalt Strike payload that evades Windows Defender. How’s that for a practical hands-on course?

No Certification Exam

The course is not preparation for or in any way associated with a certification exam, which in this case I think is a good thing. The course presents fundamental knowledge that is immensely useful in offensive security, and I think it’s best learned for its own sake rather than to add more letters after your name. I like certifications in general and have several, but I found myself not worried about covering the material for an exam and enjoyed learning the material and thinking of practical applications of it at work and in CTFs, Hack The Box, etc. instead. It’s a nice feeling.

Conclusion

I loved this course, and reenz0h is a phenomenal instructor. If it’s not been obvious so far, I’ve gained a lot of fascinating and practical knowledge that will be useful far into the future. My recommendation: take this course if you can. It’s affordable, not an excessive time commitment, and worth every second and penny you spend on it. And just in case my enthusiasm comes across as excessive or shilling, I have no association with Sektor7, their employees, or the authors of the course. Just a happy pentester with some new skills.