In late October of 2016 a large-scale cyber attack consisting of multiple denial of service attacks targeted a well-known DNS provider. The attack, consisting of a flood of DNS lookups from tens of millions of IP addresses, made many Internet sites and services unavailable to users in North America and Europe. This Distributed Denial of Service (DDoS) attack was believe to have been executed using a botnet consisting of a multitude of Internet-connected devices such as printers, camera, residential network gateways, and even baby monitors. These devices had been infected with the Mirai malware and generated several hundreds of gigabytes of traffic per second. Many corporate and educational networks simply do not have the capacity to absorb a volumetric attack of this size.

In the wake of this attack and others that have preceded it, our customers have been asking us for recommendations and best practices that will allow them to build systems that are more resilient to various types of DDoS attacks. The short-form answer involves a combination of scale, fault tolerance, and mitigation (the AWS Best Practices for DDoS Resiliency white paper, linked below, goes in to far more detail) and makes use of Amazon Route 53 and AWS Shield (read AWS Shield – Protect Your Applications from DDoS Attacks to learn more).

Scale – Route 53 is hosted at numerous AWS edge locations, creating a global surface area capable of absorbing large amounts of DNS traffic. Other edge-based services, including Amazon CloudFront and AWS WAF, also have a global surface area and are also able to handle large amounts of traffic.

Fault Tolerance – Each edge location has many connections to the Internet. This allows for diverse paths and helps to isolate and contain faults. Route 53 also uses shuffle sharding and anycast striping to increase availability. With shuffle sharding, each name server in your delegation set corresponds to a unique set of edge locations. This arrangement increases fault tolerance and minimizes overlap between AWS customers. If one name server in the delegation set is not available, the client system or application will simply retry and receive a response from a name server at a different edge location. Anycast striping is used to direct DNS requests to an optimal location. This has the effect of spreading load and reducing DNS latency.

Mitigation – AWS Shield Standard protects you from 96% of today’s most common attacks. This includes SYN/ACK floods, Reflection attacks, and HTTP slow reads. As I noted in my post above, this protection is applied automatically and transparently to your Elastic Load Balancers, CloudFront distributions, and Route 53 resources at no extra cost. Protection (including deterministic packet filtering and priority based traffic shaping) is deployed to all AWS edge locations and inspects all traffic with just microseconds of overhead, all in a totally transparent fashion. AWS Shield Advanced includes additional DDoS mitigation capability, 24×7 access to our DDoS Response Team, real time metrics and reports, and DDoS cost protection.

To learn more, read the DDoS Resiliency white paper and learn about Route 53 anycast.

— Jeff;