I see. For anyone else who doesn't have any background in this attack: memcached is an open source general purpose cache that uses sockets to cache data. From what I gather, the attack here was possible because Github engineers accidentally left the memcached port open. So the attackers were able to spam memcached with large requests, and memcached responds immediately with the full contents of the cached memory (assuming, of course, that the client is localhost).

> The memcache protocol was never meant to be exposed to the Internet, but there are currently more than 50,000 known vulnerable systems exposed at the time of this writing. By default, memcached listens on localhost on TCP and UDP port 11211 on most versions of Linux, but in some distributions it is configured to listen to this port on all interfaces by default.

Yikes!