Well, hopefully you have analytics embedded in your app. That should also give you an idea of how many users are real vs spammers. Also, what sections of your apps are being used more often. It is not too late to add the analytics to your app.

If you do not want any downloads from specific countries, why not exclude these countries for your app sale. Then you don't have to worry about span downloads, etc.

There are no spam downloads. Probably some people were curious about the topic