The UEFI specification has more tightly coupled the bonds of the operating system and the platform firmware by providing the well-defined "Runtime Service" interface between the operating system and the firmware. This interface is more expansive than the interface that existed in the days of conventional BIOS, which has inadvertently increased the attack surface against the platform firmware. Furthermore, Windows 8 has introduced an API that allows accessing this UEFI interface from a privileged userland process.