Is it possible to set a time limit on the number of written messages WITHOUT registration?

Question

Information Security

Hello. Let's say I have a guestbook. Guests are not users and do not need to register to leave a message. The problem is that they can write sooo much spam. I want to make it so that they can write no more than one message every two minutes.
What should I bind to, if not to the user_id in the database? After all, the user is not registered. to ip? You can change it (I tried restarting Tor or the extension in Chrome VPN Hotspot Shield - the ip has changed). To cookies? They can be removed and disabled altogether.

Answer 1

For these purposes, they came up with a captcha.