It has become apparent from our customers and customers of other BB Systems that there is a targeted effort being made to spam forums world-wide. Unfortunately as part of that effort it appears that ReCaptcha may have been cracked as per this page:
Until this is confirmed, we are strongly recommending that customers consider switching to the vB Q&A Verification system for now. To do this, go into the Admin CP here:
Admin CP -> Human Verifications Options -> Image Verification -> Question & Answer -> Save
Once you do that, you can click on 'Add New Question' to add a question and answer. [Note: You can use REGEX for the answer but this is not necessary.]
Question: What is the third word in this sentence?
Then click on 'Save'. Next click on 'Add New Answer' and enter:
You can add as many questions as you like and vB will choose one randomly for each registration. You can also enter multiple answers to the same question.
Also please see this thread for other things you can do to fight spam: How to Reduce Spam and Registration Bots