Protect from fake reviews on Google Play [closed]

I think the best thing to do is contact Google and make them aware of the issue.

There is a contact form on the google play site

Its also worth checking that there's not a bug in your app that stops it from opening in certain phones/devices (which may or may not be your fault, could be firmware issues). But you'll generally see users select 1 star rather than writing reviews. Remember users are lazy :)

As @64BitsPerMinute suggested in his comment, there may be some frameworks that could help detect crashes. Have a look at ACRA, or for a more managed service have a look at HockeyKit with the HockeyApp plugin. These services allow you to get crash + stack reports from your users when thins go wrong. Even if the users don't report it back to you they can click one button and send instant crash results.

Fight fire with fire. Pay some folks on vworker.com for 5 stars.

The better answer from my comment below:

... you might consider just spending the money on advertising. If your app is good enough to garner 5000 5s, then it will happen again soon on its own. Good luck!

As others have said, there may be an issue you're not aware of. You could use the Developer console to check if there's an unusually high number of reviews coming from a particular device or OS version.