When creating a shared link for a file or folder in Box, you can choose from four different options for access levels:
Anyone with the link can access the file or folder. A Box account is not required.
Only Box users with a validated email address matching your company's domain can access the file or folder via the shared link.
Only Box users invited to the folder or file (collaborators) can access the file or folder via the shared link.
This option follows whatever the default setting for your account is. You can view and change this in your Box account settings under Content and Sharing.
See Box Community articles for more information on shared links: