There is provided a computer readable medium storing a subprogram causing a computer to execute a subprocess that includes a predetermined process performed in response to a call from a caller program and a return process to return the result of the predetermined process to the caller program. The subprocess includes: an address acquisition process that acquires an access destination address to be accessed by the subprogram before executing the return process, the access destination address being assigned to the memory area of the caller program; a determination process that determines whether or not the caller program is a legitimate caller program based on the acquired access destination address; and a termination process that, if it is determined that the caller program is not a legitimate caller program as a result of the determination, terminates execution of the subprocess before executing the return process.