Well Michael, that kinda stuff is not done by pressing some magical button, you know. A solution is being looked for 
Well, you could have a message box in which an account applicant must retype a sentence next to the message box- such as "Retype this sentence in the message box".
The Chinese guy in the bot-assistance sweatshop might figure it out, but it is worth a try.
Or a button labeled "magical button", with the regular "Send" button being just a decoy.
Or both.
Just write on the screen that the Send button is fake and that Magical Button is the real one to push.