Cross-compiling is the process of building software on one system so the resulting binary runs on a different CPU architecture or operating system. For example, a developer may compile code on an x86-64 workstation for a MIPS-based embedded device, using a cross-toolchain with the right compiler, linker, headers, and libraries.
In cyber security, cross-compiling matters because many targets are routers, printers, cameras, and other embedded systems that cannot build software locally. Defenders use it to produce firmware updates, security fixes, and diagnostic tools for constrained hardware. Attackers use the same technique to create malware or implants for uncommon architectures that their own machines cannot execute natively. When cross-builds are difficult, updates are delayed and vulnerable devices stay exposed longer, making build portability a security issue as well as a development one.