While downloading APK files from sites other than the Google Play store may initially seem to be good for competition, the prevalence of malware & viruses on 3rd party stores means that less than 2% of files are downloaded outside the Play store. APK files can be easily cracked or downloaded on any Android device. It is possible to manually edit an APK file to disable certain permissions or features. These changes can be made and shared through third-party applications on a device, and may be uploaded to the Play Store for distribution to other users. APK files are divided into two types:
Primary APKs Secondary APKs
Primary APKs are used for distribution through the Play Store. They can contain the latest version of the application and are normally locked down.