Strange question, but very interesting for me :)<p>So, you you wanna check, that user is NOT a robot - you can use captcha or something, that robots can't do well.
But, if you need check, that user is a robot?<p>For example, we create some multiplayer game, were players will programming robots. [this just example, imagine, that we can't run user code on server]. In this case, user can create some UI for a this game and play game by himself. This is not good for a game balance and other game things.<p>So, we must check, that user is a robot!<p>We can send request like "calculate MD5 summ of this or that", but programmer can automatize only this part, and continue to play himself with UI.<p>So,how can we verify this?<p>ps. sorry for bad english, but i hope, you understand what I mean.