Hackers are using creative, but evil DDoS techniques such as NTP and DNS Amplification DDoS attacks. U.S. security firm Incapsula noticed surge of massive DNS DDoS attack on one of its client, peaking at approximately 25Mpps (Million packets per second) By using the same attack, the hacker succeeded in sending the malicious requests through two different servers at a rate of 1.5 Billion DNS queries per minute, amounting to over 630 Billion requests during the course of the 7 hour-long attack. Both servers used by the attacker belong to anti-DDoS service providers, one of which is based in Canada and the other in China.
Source: https://thehackernews.com/2014/05/anti-ddos-services-abuse-to-ddos-at-15.html