DNS provider UltraDNS has been under a DDoS attack for much of the day. SANS Institute s Internet Storm Center said it received multiple reports of outages and DNS resolution issues. DDoS attacks the size of this one are quickly becoming the norm. A report from Arbor Networks this week said it has already tracked more than 70 such attacks of 100 Gbps or more of bad traffic, topping out at 325 Gbps. With DNS amplification attacks, attackers take advantage of any number of the 28 million open DNS resolvers.
Source: https://threatpost.com/ultradns-dealing-with-ddos-attack/105806/