The Hostile Program is an attack virus created by the MCP, and is found in Kingdom Hearts II. It is one of the bosses at Space Paranoids. It appears to be based on the local Heartless, though it is not a Heartless.
Right after the DTD was reactivated, the Master Control Program extracted the self-destruct program for the city and began to fed it through to the outside worl through the I/O tower. However, Tron, Sora, Donald and Goofy went to the tower and interfeared with the download. They then encounter the program-incarnite, which held off its attack while the MCP asked Tron why he would help "selfish" Users. After Tron explained that it was simply a matter of friendhsip, the Hostile Program attacked. However, Tron and Sora worked together to collect bits of its data and freeze it using the Keyblade and Tron's Idenity Disk. Vunerable, the Hostile Program was defeated, but the chaos it was meant to perform on the outside world was partially complete as the wall to the Bailey had crumbled from the tremors it caused. After defeating the Hostile Program, Tron gives Sora the Photon Debugger Keychain.