The affected sites include Amazon, Twitter, Netflix, Etsy, Github, and Spotify.
It was mostly resolved at 9:20 a.m. ET, but at 12:07 p.m. ET, the issue started to crop up again, according to Dyn, one of the companies at the center of the apparent cyber attack.
At 4:16 p.m. ET, Dyn said that it was facing a third wave of attacks, CNBC reported.
Around 6:20 p.m. ET, Dyn said that the incident had been resolved, according to a status update on its website.
The issue appears to have something to do with DNS hosts — in particular, Dyn, one of the biggest DNS companies.