An unidentified person or group attacked Dyn, a large internet infrastructure company that helps people connect to websites early this morning. A second attack occurred around noon.

From 7:30 a.m. t0 around 9:20 a.m., sites like Twitter, Spotify, Airbnb, and Netflix became either inaccessible or sluggish for some users. Then, at noon, after the first attacks were resolved, a second wave of attacks against Dyn occurred.

Dyn provides a service for the internet akin to that of an address book. By taking URLs and translating them into numerical addresses, it allows servers that host websites make it easy for web users to access them.

The attacks on the servers are known as “distributed denial of service” or DDoS attacks. The locus for these particular attacks was mostly on the East Coast, and the details about it remain largely unresolved.

In recent years, the potential damage a DDoS attack can inflict on the internet has increased greatly.

“Nobody can take on the scale of these attacks these days,” Doug Madory, Dyn’s director of internet analysis, told the Washington Post.

Affected sites experienced outages during the attacks, but for the most part, major sites like Twitter and Spotify are up and running again. The identity of the attackers and the motivation behind the attacks remain unknown.

Image of areas affected by the attack via the Atlantic.