Internet users on the East Coast felt the burn Friday morning after a large-scale distributed denial of service (DDoS) attack on Dyn, an internet performance service company. The attack made it difficult for users to access popular sites like Spotify, Netflix, Twitter, Amazon, and Reddit, starting around 7:10 a.m. ET. Dyn said it “began monitoring and mitigating a DDoS attack against our Dyn Managed DNS infrastructure” around that time; and later said its service appeared to be back to normal around 9:30 a.m. ET. DDoS disturbances occur when an attacker, or group of attackers, flood a server with large amounts of fake traffic in order to shut down its system. Officials have not yet identified the source of Friday’s attack. Shortly after noon, Dyn announced that a second round of DDoS attacks had once again disrupted service to popular sites like Google, Facebook, and Twitter.