NEW YORK --A number of popular websites like Amazon and Netflix were down for some users on Friday morning in what appears to be a massive DDoS attack.
A DDoS attack -- or denial of service -- is an attempt to flood a website with so much traffic that it impairs normal service.
According to tech news forum Hacker News, the outage is a result of an attack on Dyn's DNS server. Dyn manages website domains.
Among the sites that appear to be affected include Twitter, Etsy, Github, Vox, Spotify, Airbnb, Netflix and Reddit.
"Starting at (7:00 a.m. ET) on October 21... we began monitoring and mitigating a DDoS attack against our Dyn Managed DNS infrastructure," the company said in a statement.
"This attack is mainly impacting U.S. East and is impacting Managed DNS customers in this region. Our engineers are continuing to work on mitigating this issue."
By 9:20 a.m., Dyn said "tthe services have been restored to normal."
While little information is available about the cause or who is behind the attack, companies turned to Twitter to tell customers to stay patient.
"Uh oh, we're having some issues right now and investigating. We'll keep you updated!" tweeted Spotify.
"A global event is affecting an upstream DNS provider. GitHub services may be intermittently available at this time," tweeted GitHub.
(The-CNN-Wire & 2016 Cable News Network, Inc., a Time Warner Company. All rights reserved.)