On 21 October of last year, a variety of major websites—including those of Twitter, PayPal, Spotify, Netflix, The New York Times, and The Wall Street Journal—stopped working. The cause was a distributed denial-of-service attack, not on these websites themselves but on the provider they and many others used to support the Domain Name System, or DNS, which translates the name of the site into its numerical address on the Internet. The DNS provider in this case was a company called Dyn, whose servers were barraged by so many fake requests for DNS lookups that they couldn’t answer the real ones.

Source: To Secure the Internet of Things, We Must Build It Out of “Patchable” Hardware | IEEE Spectrum