A number of popular websites were knocked offline or experienced outages this morning after a DDoS attack on DNS provider Dyn.

According to Hacker News, Twitter, Etsy, GitHub, SoundCloud, Spotify, and Shopify, among other services, were unavailable to some users. Folks accessing these sites—particularly on the US East Coast, Dyn said—experienced "increased DNS query latency and delayed zone propagation." Based on Hacker News comments, folks in Europe and Asia were not affected.

A global event is affecting an upstream DNS provider. GitHub services may be intermittently available at this time. — GitHub Status (@githubstatus) October 21, 2016

We're being affected by ongoing connection issues on the US East Coast. We'll be tweeting updates from this account! ?????? — Spotify Platform (@SpotifyPlatform) October 21, 2016

The DNS, or Domain Name System, is used to translate numerical IP addresses to more easily memorized Web addresses (like "pcmag.com"). Dyn began monitoring and mitigating the attack at 7:10 a.m. ET today. By 9:20 a.m. ET, services were "restored to normal," it said on its status page.

Github confirmed that the issue was resolved, though "we continue to monitor our systems," it tweeted.

DDoS attacks skyrocketed in 2015, and don't show any sign of slowing down. Security researcher Brian Krebs last month became the latest high-profile victim when his website suffered "a historically large" raid, which he said was revenge for exposing two hackers who provided DDoS services.

Now that the source code behind the raid has been released online, Krebs suggested "the Internet will soon be flooded with attacks."