1.35 terabits per second of traffic hit GitHub all at once, causing intermittent outages. GitHub was prepared, and the attackers backed off quickly when they realized they had met their match. GitHub had taken proactive steps to ensure any DDoS would have to jump through quite a few hoops to take the site offline. Despite the sheer size of the attack, Github had just ten minutes of intermittent downtime before anti-DDoS technology played the role of the calvary, and just eight minutes later, the attack started to drain away to nothing (by comparison)”]
Source: https://blog.malwarebytes.com/threat-analysis/2018/03/massive-ddos-attack-washes-over-github/