A series of cyber attacks this Friday took down a number of websites including Amazon, Twitter, Netflix, Pinterest, Reddit, Spotify and Tumblr. The attacks took place starting 7 a.m. and affected the US East Coast.

A series of DDoS or Distributed Denial of Service attacks made it difficult to reach the websites. A DDoS attack is done by overloading a system with requests to slow it down or shut it down.

The hackers targeted Dyn, an internet performance management company, which they cyber-sabotaged by flooding their system with junk traffic causing it to shut down.

The first two attacks happened in quick succession. CNET reported that the initial outage lasted for two hours after it was resolved by 9:20 a.m. but at 11:52 a.m., another attack was conducted. The third and final attack happened at 4:00 p.m. and resolved by 6:11 p.m.

According to reports, the company admitted that the perpetrators were "very smart". The hackers responded to every move the company made. According to them, the web outage was the result of a "sophisticated and complicated assault."

A total of 60 websites were affected by the attacks including Airbnb, BBC, Business Insider, CNN, Etsy, Fox News, Github, HBO, Imgur, National Hockey League, The New York Times, PayPal, Runescape, Slack, Soundcloud, The Wall Street Journal and Yelp. Dyn's own website was also unreachable during the attacks.

White House spokesperson Josh Earnest announced that the US Department of Homeland Security is currently conducting investigations to determine the perpetrators of the cyber attack. They are also trying to find out why Dyn was targeted by the hackers. The FBI is also conducting their own investigation.

There have been a number of DDoS attacks this year. In fact, the figure has steadily increased in the past few years. According to TechRadar, there were 85% more attacks in the last quarter 0f 2015 as compared to the same period in 2014.