The App Store is an application distribution platform for iOS, developed and maintained by Apple. It is a centralized online store where users can browse and download both free and paid apps. These apps expand the functionality of a mobile device. As of the first quarter of 2019, there were 2.2 million applications in the App Store.

Apps available in the App Store are generally written by third-party developers. Developers use Xcode and the iOS software development kit (SDK) to develop applications. Later, they submit the app to Apple for approval. Apple follows an extensive review process to check the app against the company's guidelines. If Apple approves the app, it is published to the App Store, where users can download or buy it. The strict review process makes the App Store less prone to malware, but not 100% secure.

XcodeGhost, the Apple malware that infected 50 applications within the Apple App Store, was detected in September 2015. This malware was built into Xcode, which made it harder to detect, and was reported to affect more than 500 million users worldwide. Once detected, Apple immediately removed the infected applications.