Mod tampering/Scripting

Is it possible to tamper with the mod or just make some script that adds malicious content into the mod? Because I have a RPG(Role Play Game) server and I would like to make a virus type program and then an anti-virus.

You may not modify and then redistribute ComputerCraft itself. You could, however, add a resource pack to the server that adds or replaces Lua files in the /rom (or any other) directory. You won't find much help here with malicious programs, as posting malicious code is against the forum rules.