Twitter, Reddit, PayPal, Spotify and a host of other websites suffered an outage on Friday morning (Eastern Standard Time) as a result of a distributed denial of service attack on the systems of major domain name server provider Dyn. "Starting at 11.10 UTC [Coordinated Universal Time]...we began monitoring and mitigating a DDoS attack against our Dyn Managed DNS infrastructure. Some customers may experience increased DNS query latency and delayed zone propagation during this time," the company said on its website.

According to Dyn, the east coast of the United States was the most affected by this breach. "Our engineers are continuing to work on mitigating this issue," it said, extending technical support to customers with queries. It said services were restored to normal at 1.20 pm UTC.

A DDoS attack is when an online network or service is flooded with a large volume of data from multiple sources, overloading its processing capacity and network bandwidth and causing trouble for all its users. When multiple requests come in, networks usually queue the requests to ensure that the target server does not accept requests beyond its capacity. While network admins can prevent a DoS attack by blocking a particular IP address, the quantum of data pumped into a server is much higher in a DDoS attack, making it difficult to block the multiple IP addresses.

A DNS processes users' requests to visit a particular website and directs you to the right one. If a website's DNS provider is attacked, users will not be able to access it, as is the current problem with a number of websites such as The Verge, Wired, Etsy, CNN and Recode, among others, according to Gizmodo.