How to hide email before download plugin files url ?

I want to hide email before download plugin files url because some of visitors of users can easily download the files without enter their email by going to http://www.mysite.com/wp-content/plugins/email-before-download/download.php?dl=5846idsg87b4sa8d6bf154

I want to disable direct access. When user will put their mail then they will find the link otherwise not. Is there a way to do that. I am waiting for a solution.

Regards