A massive cyberattack hindered access to many major websites across the internet on Friday. 

The attack, which came in the form of a large number of internet-connected devices, caused intermittent outages throughout the day primarily for internet users on the east coast of the U.S.

The problems started on Friday morning when Dyn — a company that hosts domain name systems for many major companies — announced that it had been the subject of a cyberattack that caused major problems for numerous websites. People reported issues with Twitter, Spotify, SoundCloud, Vox Media sites, Airbnb and numerous other sites.

Dyn said at 9:20 a.m. ET that it resolved an attack that began at 7 a.m. ET Friday. But at 11:52 a.m. ET, the company said the attack had resumed. Dyn announced on Friday night that the attacks had been dealt with. 

Brian Krebs, a security blogger who was the victim of a similar cyberattack last month, cited the firm Flashpoint and said on Twitter Friday afternoon that the attack was launched by a botnet based off of the Mirai base code, which is used to hijack internet-connected devices and use them in distribute denial of service (DDoS) attacks. 

Domain name systems (DNS) are essentially the GPS of the internet, taking the text URLs typed into a browser and figuring out where those websites’ data is located. So when a user types mashable.com in a browser, it shows them both the real Mashable and quickly locates the nearest server that hosts the site’s data. 

DDoS stands for "distributed denial of service" and is a common tactic used by hackers to take down internet-connected servers. In a DDoS attack, malicious users build a network of computers that then send massive amounts of traffic to particular servers with the goal of denying the use of those servers to other users, according to Cisco.

The source of the attack Friday was not immediately clear. 

"Hackers have no rules. One of the problems we have is that they move much faster than cyber-defenders. A DDoS attack can be launched in literally seconds, or under an hour if it's coordinated by a larger group," Steven Morgan, founder of the research firm Cybersecurity Ventures, told Mashable. "Right now, we're in the phase of figuring out where did this come from." 

This cyberattack comes at a time of heightened tension, with the US claiming it will retaliate against Russia after accusing the country of orchestrating hacks of the Democratic National Committee. 

The Department of Homeland Security and the FBI are aware of the attacks and investigating "all possible causes," DHS told Mashable. 

“The internet continues to rely on protocols and infrastructure designed before cyber security was an issue.  DDoS, especially with the rise of insecure IOT devices, will continue to plague our organizations," Ben Johnson, a chief security strategist for Carbon Black, told Mashable. "Sadly, what we are seeing is only the beginning in terms of large scale botnets and disproportionate damage done.”

The attack Friday mainly affected the eastern United States, Dyn said. 

Hacker News first noted the "massive Dyn DNS outage." The site said that if sites reported as down are working for some users, those users' machines have likely cached the DNS response for those sites.

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