I made a post that goes through the details and thought process behind writing a ransomware payload for training purposes. It goes over how the entire killchain works and how each component is written as well as defense evasion techniques employed throughout the process. Finally, it goes over how to automate the killchain so that it is reliable and repeatable.

This proof-of-concept combines a BrainFck interpreter with shell command obfuscation. It maps every 8-bit value to a BrainFck command, making detection difficult.