Recent Defeat of Zoho webform CAPTCHA

We've noticed over appx the past 2-3 weeks that the CAPTCHA field on our zoho powered webform is easily being defeated and the number of spam / junk submissions went from almost zero per day to up sometimes as many as 10 per day. This junk data shows up in our CRM and constantly needs cleaned out. All of the email addresses are registering from the "@mail.ru" domain.

Is there a way within zoho and not necessarily on the server side to block this domain or any other creative ways to prevent this spam from happening on the webform?