Block file downloads for user Problem

I have a series of file fields on a user account where users can upload files. These files need to be attached to emails (by the system with drupal_mail) and removable by the user.

But they don't actually need to be downloadable. And it would be a nice extra level of security if they can't download the files, only upload, remove and upload again.

Has anyone ever tried this (admittedly fairly niche) idea before?
As it turns out this functionality was possible with only one extra module, the Content Access module.

Select the file field on the user account. You can find them at the following path:

/admin/config/people/accounts/fields

Edit the field and under permissions select, custom permissions. You'll need the Content Access module installed for this to work.

Then in permissions you can set custom permissions for the field. To allow a user to upload and not download, you give them only the ability to create or edit their field. You don't give them the permission to view it.