NSIS (Nullsoft Scriptable Install System) is a framework dedicated to creating software installers. It allows to bundle various elements of an application together (i.e. the main executable, used DLLs, configs) along with a script that controls where are they going to be extracted, and what their execution order is. The outer layer made of a popular and legitimate tool makes for a perfect cover. The flexibility of the installer allows to implement various ideas for obfuscating malicious elements.”]
Source: https://blog.malwarebytes.com/threat-intelligence/2021/05/revisiting-the-nsis-based-crypter/