JS_Harris - 1:32 pm on Aug 10, 2013 (gmt 0)
Add a hidden input box and automatically ban anyone adding text into it. Humans will never see it but bots will occasionally step into it. Give it a nice juicy name too, such as 'web url', or give it the name of one of your real input boxes and give the real one a false name and adjust the script to only accept the false named box content. That way you get the bots which target specific contact form types too.