Mobile application security encompasses the practices, techniques, and technologies used to protect mobile apps and their data from threats across iOS and Android platforms. As mobile devices become the primary computing platform for billions of users, securing mobile applications has evolved from a best practice to a fundamental requirement. The attack surface includes authentication mechanisms, data storage, network communication, code integrity, and platform-specific vulnerabilities. A critical insight often overlooked: mobile security isn't just about protecting data in the app—it's about securing data across the entire ecosystem, from device storage to backend APIs, recognizing that the weakest link is often where the mobile environment meets third-party services or compromised devices.