WhatsApp has adopted and rolled out a new layer of security for users – built with Rust – as part of its effort to harden defenses against malware threats. Rust is a memory safe language offering numerous security benefits. We rolled out this check and were able to protect WhatsApp users from the Stagefright vulnerability much more rapidly than by depending on users to update the OS itself. Given this success, Rust was fully rolled out to all WhatsApp users and many platforms: Android, iOS, Mac, Web, Wearables, and more. C and C++ developers have specialized security training, development guidelines, and automated security analysis on their changes.