Best way to add captcha to checkout page during DoS

I know its in firewall rules, but can someone tell me exactly what I should be adding?

Would it be the website checkout URL to user path–> captcha, or can anyone tell me exactly what I should put there?

I would really appreciate some advice on this!

A post was merged into an existing topic: Any advice for an ecommerce site that is repeatedly getting hit with DoS attack?