iOS’s Walled Garden
It’s easy to forget that when the iPhone first launched, there were no third-party apps. When Apple begrudgingly added apps eventually, it did so with a slew of restrictions. This is the so-called “walled garden” of Apple’s security.
In the beginning, and even now, most apps can only see a highly curated portion of the file system on an iOS device. The result is a smartphone App Store where there are few malicious apps with any real power to do things. Importantly, Apple can also easily delete or “recall” apps that abuse or bypass its guidelines.