"The nature and source of the attack is under investigation, but it was a sophisticated attack across multiple attack vectors and Internet locations," Kyle York, chief strategy officer of the New Hampshire-based company, wrote in a blog post.
Dyn says it is monitoring for signs of additional attacks. It is still unknown who was behind the attack. The U.S. government is also investigating the incident.
Dyn is a major provider of domain name system, or DNS, services -- a key piece of Internet infrastructure that enables users to connect to websites. Many users around the world had trouble accessing popular services including Twitter, Paypal and Netflix during the attacks.
DDoS attacks have become more frequent and more powerful in recent years, but York called the cyberattacks that hit Dyn potentially "historic." Traffic from tens of millions of IP addresses -- some of which came from Internet of Things devices -- blasted the company's systems, he said.