Hide email from registration form when the user is loading information from facebook

[t18ftw]

Hi guys, i have serious problems with bots, i thinks the bots are using facebook to disable the captcha and easy registration.

for example, if im logged in facebook, i go to mysite.com/register.php and it load my facebook information, BUT i can change my EMAIL in this form. I think the bot are using the facebook connect and change the email in the form.

How i can hide the email from the form when the user is loading information from facebook?

thanks.

PD: vbulletin version 4.2.0