The Federal Trade Commission recently released an warning about fraudulent mobile apps. These apps are designed to steal personal information such as user names, passwords, credit card numbers, and other personal information.
My advise is to always get your app from an authorized app store, such as the Apple Store or the Google Store. These apps have been tested for the most part.
Another idea to try is using Google (who knows all) and searching on your app name and “fake app” to see if it has been flagged as fraudulent. Or app name and “review” to see how many complaints there are.
For more information from the FTC and US-CERT: