There is a program called Quick Macro, it can be programed to do just about anything you can do with a keyboard or mouse, and it can use direct machine language to operate at a faster speed, while this is not the only use or program, a Bot can be made to mimic just about any person and do it on its own automatically, I have seen them sign up to a forum in droves (a good sign of an impending attack) wait for a confirmation e-mail then make its own post or several to mimic a real member, then after a sleeper timeout start spamming.
Very hard to detect or stop.