A flaw in the implementation of the UDP protocol for Memcached servers can allow anyone to launch a massive Distributed Denial of Service (DDoS) attack with little effort.
The problem was first discovered by security researchers at content delivery network (CDN) specialist Cloudflare. Since then, CDN specialist Akamai and security provider Arbor Networks have also published their findings.
Memcached is a Web-based massive memory cache for database-drive sites, such as websites, that caches the most frequently retrieved data and keeps it in memory rather than getting it from the hard disk over and over again. It is a combination of open-source software and standard server hardware that consists of memory, memory, and more memory.
Source: NW Security 1