A massive online attack left many major internet websites unreachable on Friday morning.

New Hampshire-based company Dyn was a victim of the DDoS attack which began at 7:10 a.m. ET. The attack blocked websites such as Netflix, Spotify, Twitter, and Amazon from various users on the East Coast. The company reported that it had resolved the issue at 6:17 p.m. ET on Friday.

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Dyn offers hosting services for Domain Name System (DNS), which links a website's name to its IP address.

In an interview with ABC News, Kyle York, Chief Officer at Dyn, said that the attack seemed very complex and involved "tens of millions" of IP addresses. He also stated that the attack might have been carried out by a network of botnets.

Dyn revealed that the attack took place in two waves, occurring within a couple of hours of each other. However, it is not yet clear whether any major website was compromised by the second wave of the attack. York said that the second wave has "ebbed and flowed" since its start.

According to the White House press secretary, the attacks are now being investigated by the Department of Homeland Security. The FBI is also said to be involved in the investigations.

This DDoS attack follows another DDoS attack which occurred earlier this month, targeting the website of independent cybersecurity journalist Brian Krebs. It is believed that both attacks were conducted using Mirai Botnet. It is also possible that the attacks piggybacked on compromised Internet of Things (IoT) devices. The code used for building the botnet was later leaked online.