The sole purpose of a crypter is to decrease the detection rate of an executable, ideally to the point where it is not detected by any AV.
So, why is PEunion not FUD?
PEunion was FUD as of September 2021. However, any crypter will remain FUD only for a certain period of time. This is especially the case for a crypter that is public & free.
Is it possible to fix this and make PEunion FUD?
It is possible to address detection issues and fix them. However, keeping PEunion FUD long term is a job that would require several hours of work each day.
This is time that I am just not going to invest. Developers who provide a crypter that is guaranteed to be FUD will typically sell it and put in the time to continually make proper modifications.
What is the purpose PEunion then?
PEunion is a fully functional crypter alongside with a lot of useful features. The code of the stub can be modified by any means necessary to evade static and behavioral signatures. Please read the main page to learn about the two-layer architecture and how it helps minimizing the amount of code that needs to be changed in order to fix detection issues.
The bottom line is: With sufficient programming and reverse engineering skills, you will be able to derive your own "private stub". As long as you use non-distributing AV scanners and keep the stub to yourself, it will remain FUD much longer as compared to changes that I make publicly available to everyone.
If you do not have sufficient skills to do this, I would recommend looking for alternative products.