Red Hat issued best practice guidelines for users about the memcached vulnerability that has lead to record breaking DDoS attacks.
"Red Hat is aware of DDoS (Distributed Denial of Service) amplification attacks being performed by exploiting memcached servers exposed to the public Internet. These attacks take advantage of memcached communication using the UDP protocol for transport. The attack is effective because of the high amplification ratio—a request with the size of a few hundred bytes can generate a response of a few megabytes or even hundreds of megabytes in size."
You can see Red Hat's best practice recommendations on the memcached vulnerability here.