I know how they work, I'm asking GP to name one that he could have used. There isn't actually much "out there" that is undetectable. You'd likely have to write your own, which is highly non-trivial.
Obviously undetectable isn't true, but i'd guess that kbeast is likely to go undetected in all but the most prepared operations. Forensics shouldn't count since you already know you're fucked by then.