To provide an optional code execution system for prevention of analysis and operation of computer executable code.

In the system, a device for preventing the operation of a computer program is provided with: a code pool management module 110 for managing a code type to be loaded on the memory of a computer instead of a program; a code control module 120 for executing a control operation to select and transmit a specific code from among the codes stored in the code pool management module 110; and a code execution module 130 for loading the specific code transmitted from the code control module 120 on the memory, and then, for executing it as a portion of the existing program.