To reliably protect users or systems from a program prepared by a malicious developer. Provided is a processing system configured to process a program transmitted from outside through a wired or wireless network. The processing system includes: a reception module configured to receive the program; an addition module configured to add to the program a gate component that restricts a process of attacking a user or the system; and an alteration module configured to alter, in the program, a code having a certain keyword or syntax to change a destination to be referred to by the code having the keyword or syntax to the gate component.