Check the user agent. Many bot writers never bother to change it. PycURL, Java, urllib, etc. If you only want humans on your website, only accept browsers used

Check the user agent. Many bot writers never bother to change it. PycURL, Java, urllib, etc. If you only want humans on your website, only accept browsers used by humans. Sure the botter's may clone IE's user-agent string, but you'll still stop the lazy ones.