I recently published my first course on Udemy and decided to keep it free for demo. What concerns me is that it got over 1400 enrollments in just 5 days but only a handful of them have started the course. When I checked the student profiles of other students (who haven't yet started with the course), I found that they have enrolled in thousands of courses. It seems that there is some kind of bot that is just made to enroll in the free courses. 

How can we get rid of them so that we have only genuine students? 

Has anyone faced similar issues?