Dyn warns customers that a third cyber attack is currently underway

Internet traffic company Dyn on Friday warned of another cyberattack after websites and services across the East Coast were shut down earlier in the day.

Dyn told CNBC Friday afternoon the attacks are “well planned and executed, coming from tens of millions IP addresses at same time.”

“We have begun monitoring and mitigating a DDoS attack against our Dyn Managed (Domain Name System) infrastructure. Our Engineers are continuing to work on mitigating this issue,” Dyn said on its website at 11:52 a.m. ET.

A Distributed Denial of Service (DDoS) attack is when a web service is intentionally overwhelmed by traffic from many sources. It is a common method for digital assaults.

Dyn also said the attack impacted its DNS advanced services monitoring for customers, but it later resolved the issue.

It was not known who was behind the distributed denial of service attack.

The Department of Homeland Security told CNBC that it is “looking into all potential causes” of the attack. NBC News reported that one U.S. intelligence official said North Korea had been ruled out as a suspect.

The White House said U.S. authorities are monitoring reports of attack on the internet services company and whether it is a “criminal act,” according to Reuters.

Many prominent websites including Amazon, Twitter and Spotify were shut down for nearly two hours Friday morning by an earlier denial of service attack. CNBC.com was also affected. Amazon reported later that it was once again having service issues but resolved the problem.

Later in the day, Netflix and PayPal reported that they are experiencing issues, while Spotify and said some of its members were having trouble accessing their website.

Dyn said the earlier attack started at 7:10 a.m. ET. It affected Dyn’s Managed DNS infrastructure, which is the system that directs users to the correct webpage.

Dyn said the services had been restored to normal after the initial attack by 9:20 a.m. ET.