Suggestion: remove current Torn Text captcha (which is the weakest captcha system I've ever seen) and replace it with a proper captcha (re-captcha like).
Also require captcha solving every once in a while for STOCKS , training and attacking
Then to track down bots it would be enough to track people who consistently fail captchas / stop playing / close browser / close connection / change browser / change connection / change page as soon a captcha is encountered