There are perfectly legal sources with which you are not aware.
Secret sources? I smell bull****.
Answer the question, it is an easy one. Where did you get "hundreds"
of movies with a license to copy them?
I don't know the details because I've never done it but apparently
sources of movies such as Amazon allow you to download a complementary
digital copy of the movie *if* you have purchased a hardcopy (DVD).
There are also other sources for downloading digital copies such as
something called "VUDO" but again, I don't know anything about it.
Never did it.