Twitter, Spotify and Reddit, and a huge swath of other websites were down or screwed up this morning. This was happening as hackers unleashed a large distributed denial of service (DDoS) attack on the servers of Dyn, a major DNS host. It’s probably safe to assume that the two situations are related.
In order to understand how one DDoS attack could take out so many websites, you have to understand how Domain Name Servers (DNS) work. Basically, they act as the Internet’s phone book and facilitate your request to go to a certain webpage and make sure you are taken to the right place. If the DNS provider that handles requests for Twitter is down, well, good luck getting to Twitter. Some websites are coming back for some users, but it doesn’t look like the problem is fully resolved.