The scope of this thesis is the study of Malware Analysis on Windows environment in a systematic and detailed manner, based on SAMA methodology. Furthermore, taking under consideration the ENISA guidelines, a laboratory was created, which is modular and capable of isolating the infected VMs, providing them with Internet connection or simulating one when the appropriate rules are applied. An unknown sample was selected which ended up being a variant of “Agent Tesla” RAT as the use cas. Extensive effort was given in reversing the malicious code and observing its behavior to fully understand the intentions of each sample. Beyond the core functionality are findings such as the communication means, the servers used to download malicious code, evasive and Anti-VM techniques, as well as techniques to bypass malware defensive mechanisms.