Cyber attacks are getting evil and worst nightmare for companies day-by-day, and the Distributed Denial of Service (DDoS) attack is one such attacks that cause a massive damage to any service. Recently, the Internet witnessed a record-breaking largest DDoS attack of over 1 Tbps against France-based hosting provider OVH, and now the latest victim of the attack is none other than Dyn DNS provider. A sudden outage of popular sites and services, including Twitter, SoundCloud, Spotify, and Shopify, for many users, is causing uproar online. It's because of a DDoS attack against the popular Domain Name System (DNS) service provider Dyn, according to a post on Ycombinator. DNS act as the authoritative reference for mapping domain names to IP addresses. In other words, DNS is simply an Internet's phone book that resolves human-readable web addresses, like thehackernews (.) com, against IP addresses. Dyn DNS is used by many websites and services as their upstream DNS provider, including Twitter, Spotify, SaneBox, Reddit, Box, Github, Zoho CRM, PayPal, Airbnb, Freshbooks, Wired.com, Pinterest, Heroku and Vox Media properties. All of these sites and services are reportedly experiencing outages and downtime, either completely or partially.