Created my survey and immediately had 10 responses of which none were valid

I hit publish and shared on FB and within a couple of minutes, had my 10 responses for the month of which none of them were valid. It was the same person filling it out 10 times.

I don’t mind paying for typeform and upping my monthly allotment of services but now i’m concerned someone else may come along and fill ‘er up. I get it...the link is public but wondering if there’s anything I can do to help try to prevent this?

Thank you!