Cloud sharing - security

I intend to use My Cloud also for sharing large files with selected others, but I am not sure how safe this is. I am starting off with private use and then hope to expand to file sharing with business partners.

I noticed that a new user who signs in for the first time, will see the names of registered users +/-  admin rights. A new user has the potential to try passwords with the given user names. Is that assumption correct or can this be done differently, or is this only happening for devices on the home network?

How safe is it to have the backup files on the same  “My Cloud”?

Only the users that you select to have access, are able to open the private shares you create, by default the Smartware backup share is public, but you can also make it private. For more information on how to create private shares, check page 56 of the manual.