One of my clients has been being hit with a bot that is a form filler. The bot is called "www.textron.com/testBot" and it filles out forms like crazy. I have tried using a robots.txt file - but since this is one that probably changes name all the time (textron makes highly protected armored vehicles used in Irq) so that's why their name is being used.
but any thoughts as they have received almost a thousand this week.
As a last resort - maybe one of those submissions that use a verify graphic- that is cheap or open source?