advait, I may not be reading your question the same way as others, but if you are using something like FormMail to do forms processing, I would suggest switching to a secure replacement that can block data by domain or IP. That way you can force the use of your web interface as the data entry point. The nms FormMail replacement allows you to tell it which sites can send data to your form processing code.

Now, at this point, whether you block mechanization is another issue entirely.