Denial of Service attacks can encompass a number of different tactics, all aimed at impacting the availability of your applications and/or infrastructure. In Defending Against Denial of Service Attacks we described both network-based and application-targeting attacks. In this paper we dig much deeper into application DoS attacks. For good reason – as the paper says:

These attacks require knowledge of the application and how to break or game it. They can be far more efficient than just blasting traffic at a network, requiring far fewer attack nodes and less bandwidth. A side benefit of requiring fewer nodes is simplified command and control, allowing more agility in adding new application attacks. Moreover, the attackers often take advantage of legitimate application features, making defense considerably harder.

We expect a continued focus on application DoS attacks over time, so we offer both an overview of the common types of attacks you will see and possible mitigations for each one. After reading this paper you should have a clear understanding of how your application availability will be attacked – and more importantly, what you can do about it.

We would like to thank our friends at Akamai for licensing this content. Without the support of our clients our open research model wouldn’t be possible.

To sum up, here are some thoughts on defense:

Defending against AppDoS requires a multi-faceted approach that typically starts with a mechanism to filter attack traffic, either via a web protection service running in the cloud or an on-premise anti-DoS device. The next layer of defense includes operational measures to ensure the application stack is hardened, including timely patching and secure configuration of components. Finally, developers must play their part by optimizing database queries and providing sufficient input validation to make sure the application itself cannot be overwhelmed using legitimate capabilities.

Keeping applications up and running requires significant collaboration between development, operations, and security. This ensures not only that sufficient defenses are in place, but also that a well-orchestrated response maintains and/or restores service as quickly as possible. It is not a matter of if but when you are targeted by an Application Denial of Service attack.

Direct Download (PDF): Defending Against Application Denial of Service Attacks