How does a cryptor work which can make doc or similar formats from exe?

Question

C++ / C#

I think I didn’t explain the essence of the issue well ... Once I saw a cryptor / hiding exe, it was sold and I became interested ... How it works.
About the program: you throw a file into it, for example, belochka.exe, choose an extension, for example, doc, and magic happens! The program makes belochka.doc))

Answer 1

There are two different tasks.
1. Simple. Carry the program through the security system, provided that your computer is a “safe haven” and can be safely decoded and launched. For example, to confuse the Gmail antivirus.
2. Difficult. Your computer is no longer a “safe haven”, it has security systems, and you need to somehow bypass them. Or, for example, we are spreading a virus, and a vigilant user is in the role of a security system.
The first task in the simplest case is solved by changing the extension. You can come up with more complex methods so that the antivirus says: this is really a DOC.
To solve the second problem, it is necessary to find an exploit like "arbitrary code execution" in the program (Word, WinRAR, etc.).