To secure your site you can add reCAPTCHA to your site.
1. Go to Dashboard » Reservations » Security Settings.

2. Copy the Public Key from Google reCAPTCHA and paste it into the field.
3. Copy the Secret Key from Google reCAPTCHA and paste it into the field.
4. Choose Theme for your site.
5. Choose language of reCAPTCHA.
6. Enable OR Disable spam verification with reservation form on front-end.
7. Click on Save Changes.