It seems that the newsgroup indexes have gone underground, with lots of small tight-knit private communities trading encrypted files.
Just doing random usenet browsing there are literally billions of files with randomly generated names holding encrypted RAR files. I'm guessing that the overwhelming majority of these are pirate material.
However, I was, for a bit, working on a usenet data backup program. It would take your files compress, encrypt, PAR and then upload to usenet, as a ghetto cloud backup system. Just remember what you called the files and what the password was.
I used it a couple of times to broadcast a bunch of home movies to friends, where the file sizes were excessive for a drop-box, and various people had unreliable connections and were finding it difficult to download.
I don't really have much use for usenet these days. However, I used to use a dutch provide called extremeusenet and still have some pre-paid time remaining on the account. I used to share an account with a bunch of family/friends, as this provider allowed unlimited account sharing, subject only to the speed limit specified in your account.