What should be done?
If you are an Operator, update or deploy your Exploitable Port Filters. Add TCP/UDP port 11211. You can find details here:
If you are an enterprise, ask your upstream ISP if they are deploying Exploitable Port Filters AND look through your firewall rules to add them to your network. Layered security means it is prudent to ask your ISP to do their part while you do your part.