WhatsApp has implemented a new security layer for its users, utilizing the Rust programming language, as part of an ongoing effort to combat malware threats. With over 3 billion users, WhatsApp's media sharing functionality has been particularly targeted for improvement. In the past, vulnerabilities like the 2015 Android "Stagefright" bug highlighted the need for robust media file protections. This realization led WhatsApp to enhance its media handling by creating a Rust version of its existing C++ library, “wamedia,” which processes MP4 files. By doing so, they aimed to ensure user safety even when underlying operating system vulnerabilities could not be patched immediately. The transition to Rust allowed WhatsApp to replace 160,000 lines of C++ code with 90,000 lines of Rust, resulting in better performance and lower memory usage. The rollout spanned multiple platforms, including Android, iOS, and web browsers. WhatsApp’s security strategy now includes checks for non-conformant file structures and high-risk file types, collectively known as the “Kaleidoscope” system. This system is designed to protect against malware hidden in seemingly harmless files, like images or PDFs, by flagging potentially dangerous content for special handling. WhatsApp's broader security strategy also involves default end-to-end encryption, transparent key technology, and a proactive approach to reporting vulnerabilities. They conduct thorough risk assessments through audits and fuzzing, focusing on minimizing attack surfaces and investing in secure coding practices. Their goal is to shift towards memory-safe languages like Rust for new code, addressing vulnerabilities that often arise from C and C++ code. WhatsApp plans to continue expanding Rust’s adoption across its security frameworks, aiming to enhance user safety significantly.