A system and method to reduce external access to hypervisor interfaces in a computer system, thereby reducing the possibility of attacks. In a preferred embodiment, addresses for calls are used to fill a table, where the addresses are specifically selected for a requesting computer. For example, in one embodiment, a routine searches for the adapter type of a requesting computer and populates the table with calls specific to that type of adapter. Other types of calls are not put in the table. Instead, those calls are replaced by routines that will return an error. In other embodiments, the operating system type is used to determine what addresses are used to populate the table. These and other embodiments are explained more fully below.