CAPTCHA
Add reCAPTCHA or Turnstile to your form and block submissions when verification fails.
Edge rules
Use a reverse proxy or CDN rules to block suspicious traffic or known bot patterns.
Server-side validation
Post to your own API first, validate the request, then forward to Formbase.
Honeypot fields
Add a hidden field and treat filled submissions as spam.
Combine multiple techniques for the best results. CAPTCHA + rate limiting is a common baseline.