The Monster Possession Program is a program that Franz Hopper used the first time in the episode The Key. He used it to help Ulrich and Aelita to recover Aelita's missing fragment. He possessed two Mantas in order to get them closer to the glowing fragment. It allows the user to gain control over one or more monsters.
During possession by the program, the monster glows a bright blue-white aura. The Franz-possessed Mantas were destroyed by falling blocks once Lyoko began to crumble. (The Key)