I was going to ask the same question. Besides reading every line of machine code? The only way I can think of is monitoring its traffic and looking into anythi

I was going to ask the same question. Besides reading every line of machine code? The only way I can think of is monitoring its traffic and looking into anything fishy from there. But even that isn't conclusive. Maybe the backdoor listener is behind a complex port knocking sequence? There's really no way to tell.