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SDN and Security: Network versus Applications

As attackers move up the stack, so must defenders

That attackers are moving "up the stack", toward the application layer, should be no surprise. Increasingly, network layer attacks are a distraction; a means to engage security professionals attention while the real target - an application - is attacked. Even when this is not the case, the tendency to attack at the application layers is increasing because honestly it's cheaper in terms of resources to take out an application using application layer attacks than it is to do so at the network layers. Sure, an attacker might not be able to completely eradicate a company's presence from the Internet, but it can take out critical applications that make it appear as if they've disappeared, which has pretty much the intended effect - costly downtime due to loss of revenue, brand damages, and probably a few blown aneurisms due to stress.

Don't take my word for it, though. Here's a sampling of warnings and predictions from around the industry:

“An increasing number of application-layer attacks, which older DDoS detection and mitigation infrastructure can’t identify and block, are forcing companies to make new investments in DDoS solutions.”1

"The challenge with application-layer attacks is to distinguish human traffic from bot traffic, so DDoS mitigation providers often use browser fingerprinting techniques like cookie tests and JavaScript tests to determine if requests actually come from real browsers. Launching DDoS attacks from hidden, but real browser instances running on infected computers makes this type of detection very hard.

“We’ve been seeing more and more usage of application-layer attacks during the last year,” Gaffan said, adding that evasion techniques are also adopted rapidly."2

"In a report titled, “Arming Financial and E-Commerce Services Against Top 2013 Cyberthreats,” Gartner forecasts that 25% of ALL DDoS attacks in 2013 will be application-based."3

The inevitably of application layer attacks on your very own applications is why it's increasingly important to understand the difference between network security and application security. The two are not the same, and they require very different solutions.

Increasingly, it is posited that SDN is well-suited to answer the ever presence and growing challenge attackers present to security ops. Given its dynamic and software-defined (separated control plane) nature, that makes sense - when we're talking about the network, at least.

SDN and Security
It is important - very important - to remember that SDN architectures, by design, only provide the visibility and control required to implement security at the lower order layers of the network stack. Specifically, layers 2-4. That's data link, IP, and TCP (and sometimes UDP) for the uninitiated.

Note that nowhere in that list is "application" mentioned. The application layer is way up at the top - at layer 7 - and in 64% of applications4 that means HTTP.

Interestingly, there's nothing stopping an SDN "application" from inserting itself into the SDN controller (via the northbound API) and providing application layer security by acting as a full proxy and inspecting every single packet. Well, nothing except for scalability and performance of the SDN controller, which was not designed to be a part of the active data path. The architecture was designed to focus on the network, on forwarding packets and managing flows, not inspecting application layer transport protocols and the data it carries. But that's exactly what's necessary to provide the kind of application layer defenses required in this brave, new application attack-based environment. Inspection of payloads, not packets. Evaluation of clients, not connections.

network-versus-application-security

This is not to say that an overarching SDN architecture can't provide for both network and application layer security.  An integrated solution comprising both network and application-layer elements will ultimately provide the comprehensive top-to-bottom (of the stack) security desperately needed to defend against attackers. What you won't see are SDN applications that provide true application-layer security. For that, you'll need focused data path elements and, most likely, an application service management and orchestration component to control those elements. The application service management  and orchestration component then integrates with the SDN controller (control plane) and executes via service chaining (data plane) to enable defense of the entire network - and applications.

sdn-big-picture

What's most important to remember is that network security is not application security. Whether you're trying to figure out how SDN is going to fit into the larger information security architecture or just trying to prepare for the next wave of attacks, evaluate your readiness for both types of security measures and policies.

1. Application-layer attacks sparking new investments in DDoS solutions

2.  Application-layer DDoS attacks are becoming increasingly sophisticated

3. Gartner: Application Layer DDoS Attacks to Increase in 2013

4. Based on F5 iHealth statistics from 55,270 BIG-IP systems (Aug 2013)

More Stories By Lori MacVittie

Lori MacVittie is responsible for education and evangelism of application services available across F5’s entire product suite. Her role includes authorship of technical materials and participation in a number of community-based forums and industry standards organizations, among other efforts. MacVittie has extensive programming experience as an application architect, as well as network and systems development and administration expertise. Prior to joining F5, MacVittie was an award-winning Senior Technology Editor at Network Computing Magazine, where she conducted product research and evaluation focused on integration with application and network architectures, and authored articles on a variety of topics aimed at IT professionals. Her most recent area of focus included SOA-related products and architectures. She holds a B.S. in Information and Computing Science from the University of Wisconsin at Green Bay, and an M.S. in Computer Science from Nova Southeastern University.