On Friday, a massive distributed denial of services attack (DDoS) knocked out access to a number of major websites. Although the incident appeared to target the U.S., its effects rippled out internationally, reportedly even reaching major banks and supermarket giants in Australia. While facts are still emerging, it seems the attack centred on Dyn, a domain name systems (DNS) provider that essentially acts like a phone book for major sites such as Twitter, Amazon, Tumblr, Reddit and Spotify.