Free apps from the Amazon Appstore are safe to download, as long as they are downloaded directly from the store itself. These apps go through a similar vetting process as those on Google Play.
Although apps from the Amazon Appstore are safe, the installation process introduces security vulnerabilities to Android users. To install apps, users must change the security settings of the Android device to install apps from unknown sources, a process known as side-loading. Once set, the Android device allows a user to install an app regardless of its source, not just from the Amazon Appstore. There is no current Android feature to only allow apps from a specific marketplace.
The majority of malware comes from third-party sites, though it can also be sent as attachments in emails. Usually, an Android device defends the user by refusing to install any application that did not originate from Google Play. However, this feature is disabled in the process of installing apps from the Amazon Appstore, creating a security vulnerability. There are thousands of malicious Android applications currently in circulation, and the majority come from third-party sites.
To avoid this issue, users should re-enable the security feature and disallow installations from unknown sources as soon as the application from the Amazon Appstore is installed. This protects the device when not loading intended applications.