[Flask] Handling web requests from blacklisted IP addresses?

[Keith MacDonald]

I've recently built a website based on Python and Flask. Everything's fine (thanks Flask). 

But being cautious, in case I made mistakes with the Routes, I've been logging any 404 error messages, along with the IP address the request came from. By accident, it seems to be working well as a malicious-probe detector. I'm seeing many 404 error messages caused by blacklisted IP addresses trying to find and access PHP admin pages (which don't exist). 

Should I care about this? 
I'm imagining I could add a table of blacklisted IP addresses quite easily, and check the IP address before routing any pages. 
But then what?
Should I send all requests from  blacklisted IP addresses to a special page? 
Or a completely blank page?
Or redirect them to some hell-hole on the internet?
Or what?

Any suggestions gratefully received.

Keith MacDonald