Hi CyberSecurityEasyDotCom123,

We take spam and general security very seriously at Calendly. If you are a Calendly user and are concerned about malicious actors taking advantage of you booking page, there are a couple of  potential workarounds.   

1. I would consider discussing with your web administrator what your options are for blocking IPs.
2. Or you can consider the Routing form option:

Getting started with Routing Forms

  Then create logic that looks like this:  

Whenever they use their email address it will not direct them to book but to the "Thank you for your interest" page.