Distributed computing on the Internet presents new challenges and opportunities for tools that inspect and modify program binaries. The dynamic and heterogeneous nature of the Internet environment extends the traditional product development process by requiring program development tools like these, which were once used only internally, to work in live environments too. The concept of compilation process must be expanded along with the capabilities of the binary tools. This paper presents Vulcan , a second-generation technology that addresses many of these challenges. Vulcan provides both static and dynamic code modification and provides a framework for cross-component analysis and optimization. It provides system-level analysis for heterogeneous binaries across instruction sets. Vulcan works in the Win32 environment and can process x86, IA64, and MSIL binaries. Vulcan scales to large commercial applications and has been used to improve performance and reliability of Microsoft products in a production environment.