General virtual hosting via lightweight user-level visualization

The abundance of computing resources in current systems makes it technically feasible to run services for multiple Internet sites on a single machine. However, in the UNIX security model, a vast majority of services must be run with superuser privileges. This increases security risks considerably when numerous services are running in parallel, making the isolation of services a critical issue. Virtual hosting systems have been implemented at the application level and at the operating system (OS) level and by running services in isolated full-scale virtual machines. We present a middleware approach to general virtual hosting that does not require modifications to the OS or the application. While completely implementable in the user-level in UNIX-like OSes, our system allows secure deployment of services, even when they are executed with superuser privileges.