Ofc, the code modifications and additional data are not public, neither they are online. And we are talking air gap transfer.

I repeat: the second you are online, you are cooked. Everything else is BS, probably somebody is trying to sell you something.

All you can do is to find compromise depending on the classification of the data.

And as I said, if you are making it too much hell for attackers, they will switch to social engineering.

Come on...