The work explores different categories of malicious software with focus on ransomware. The theses categorizes ransomware among other malware and explains possible ways of its spreading and action. The paper also explains basic cyber security concepts and the ways malware spreads and attacks. Main principles of cryptography, cryptographic functions and algorithms are explained in detail, starting with AES cypher and onto RSA and ECC algorithms. The second part of the theses gives detailed implementation plans, concepts and, most importantly, code. Language for ransomware implementation is Go and command-and-control web application is written in JavaScript using NextJS framework. To make sure server runs easily on any machine, it is containerized using Docker virtualization tool. It can be run in conjunction with Tor Hidden Services also ran using Docker. The last part of the paper focuses on recovery and prevention of such attacks. Focus is set on Antivirus software and ways it detects and defeats malware. But since malware doesn’t go down without a fight, possible evasion methods are also discussed and shown. The paper introduces the concept of Crypters and Encoders as well as virtualization evasion and detection techniques employed by the malware writers. The code is located at Github repo: https://github.com/kula124/Diplomski