Fighting advanced DDoS attacks

The National Institute of Standards and Technology (NIST) is working with the Department of Homeland Security (DHS) Science and Technology (S&T) and industry to research and develop approaches to DDoS detection and mitigation, which are becoming more sophisticated.

Gregory Hale, ISSSource

Distributed Denial of Service (DDoS) attacks are on the rise and it is becoming more difficult to combat them as they get more sophisticated and intense. That may change in the future as the National Institute of Standards and Technology (NIST) is working with the Department of Homeland Security (DHS) Science and Technology (S&T) and industry to research and develop novel approaches to DDoS detection and mitigation, techniques to test and measure the effectiveness and impact of DDoS/spoofing mitigation techniques, and to develop deployment guidance for such techniques.

The rapidly growing threat of DDoS can end up characterized by the orders of magnitude increases in the bandwidth of such attacks (from 100s of millions bits per second, to 100s of billions bits per second) and the growing range of targets (from e-commerce sites, to financial institutions, to components of critical infrastructure).

The methods of launching massive DDoS attacks are also changing, from the mass use of infected individual PCs, to the use of powerful, richly connected hosting facilities and /or the use of mobile applications.

Reflection, amplification DDoS attacks

Reflection/amplification attacks represent a specific form of DDoS that is problematic.

Reflection attacks rely on the ability of an infected/controlled host to spoof the source address of its queries to powerful Internet servers (e.g., DNS servers). By placing the address of the eventual attack target in the source address of its queries, reflection attacks use the resources of the Internet's own infrastructure against itself. These attacks are even more dramatic, when the attacker can use a very small query to generate a much larger response to be relayed toward the eventual target. This scaling up of input energy to size of response is called "amplification", and recent events have documented attacks of this type reaching 300+Gbps.

The servers exploited in such attacks include DNS servers (estimated to be ~30 million vulnerable to exploitation), and Network Time Protocol (NTP) servers (estimated to be ~1 million vulnerable). While we can and should focus on improving the implementation and configuration of these servers and applications protocols to avoid their exploitation in DDoS attacks, the scope of that problem is vast and many of these severs are in equipment and networks not actively maintained.

For well over a decade, the industry had developed specifications of techniques and deployment guidance for IP-level filtering techniques to block network traffic with spoofed source addresses. These techniques vary greatly in their scope and applicability. Some techniques are primarily focused on ingress filtering at the stub-boundaries of the Internet and typically have the granularity of Internet Protocol (IP) prefix filtering. These techniques are often referred to as "BCP38" after one of the original internet engineering task force (IETF) specifications in this area, but include a range of additional techniques not covered in BCP38 or its follow on BCP84.

Deployment of the anti-spoofing techniques can be viewed as a cycle of configuration, performance analysis, and finally monitoring and verification of the deployed techniques.

Goal-oriented work

NIST's goals are to work with the community to document and quantitatively characterize the applicability, effectiveness and impact of various approaches to filtering spoofed IP traffic streams and then to develop consensus recommendations and deployment guidance that can drive adoption in federal network environments and throughout the industry.

NIST will survey the state of the art in source address filtering techniques and develop methods of quantitatively characterizing their scope of applicability, effectiveness, deployment considerations and potential impact on network performance and reliability. Emphasis will go to identifying how different network structures impact configuration and performance. In particular, configuration and performance distinctions will be analyzed for edge networks (e.g. a bank, agency, etc.), small scale transit (university, larger agency, regional exchange point), and large-scale transit networks (national and global ISP's) will end up analyzed.

NIST will develop deployment scenarios and testing infrastructures to empirically measure the scaling, performance and robustness properties of current filtering techniques. Edge networks and small-scale scenarios will also undergo measurement on a test bed of current state of the art implementations.

NIST will also develop comprehensive technical guidance and a strategic roadmap for the ubiquitous deployment of source address filtering mechanisms. The envisioned scope of this guidance will focus on data traffic and will address plans for incremental deployment and continued maintenance of the proposed mechanisms.

Gregory Hale is the editor and founder of Industrial Safety and Security Source (, a news and information Website covering safety and security issues in the manufacturing automation sector. This content originally appeared on Edited by Chris Vavra, production editor, CFE Media, Control Engineeringcvavra(at)

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