Back in the early 2000s lots of websites had an unauthenticated "guestbook" feature where visitors could leave a message. As soon as Google and page rank became a thing bots would drive by and leave links to the website they were promoting. The idea was to increase the number of backlinks and thus improve your Google rank.

The fix to this was shockingly simple. Add an input box with a standard name like "title" and then hide it with CSS. The bots would always provide a value for every input. If you saw a value for your hidden input you returned 200 but never added the post to your website.