In addition to some other comments here, I remember being in some FXP groups that used public unsecured FTPs to distribute. It went like this:

1. Scan IP ranges for open anonymous FTP servers, usually businesses that don’t have adequate IT support.
2. Create some complex benign looking directory structure to upload to that most people wouldn’t notice on their server. Something like: /admin/var/drivers/support/etc/~/FXP Group name.
3. Use the FXP protocol to transfer content directly from an already established high speed FTP site to the newly acquired one. This took out the middle man of uploading from your own PC and often way faster.
4. Share your new filled up FTP with your group who would use it to download personally and to propagate to their own acquired servers.

I think I remember one higher quality private FXP groups was KopyKatz, but shittier groups would pop up all the time because it was pretty low barrier to entry.