Making GitHub’s edge infrastructure more resilient to current and future conditions of the internet and less dependent upon human involvement requires better automated intervention. We’re investigating the use of our monitoring infrastructure to automate enabling DDoS mitigation providers and will continue to measure our response times to incidents like this with a goal of reducing mean time to recovery (MTTR). We’re going to continue to expand our edge network and strive to identify and mitigate new attack vectors before they affect your workflow on GitHub.com. We know how much you rely on GitHub for your projects and businesses to succeed. We will continue to analyze this and other events that impact our availability, build better detection systems, and streamline response.

DDOS or Distributed Denial Of service refers to crashing server by sending tons of requests from different systems. The systems are usually infected with trojan or malware and all the online systems are made to send continuous requests at one particular time flooding the server.Memcached server are more responsive than usual servers since they have improved memory caching.Attackers spoofed github's IP and took control of memacached servers of Github from UDP port 11211 . Github stated that these servers are inaccessible to the general public. They used it to amplify traffic and attempted to crash the server. The amplification was around 50 times. This lead to github being attacked at a volume of 1.3 Tb/s.This is the largest DDOS attack ever recorded in the history. Astonishingly it took Github approximately just 5 mins to recover. Github was down on 28th Feb between 17:21 UTC and 17:26 UTC.As quoted from https://githubengineering.com/ddos-incident-report/