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Software-defined networking: Exploring SDN security pros and cons

Matthew Pascucci offers an intro to software-defined networking and explains why SDN security relies on securing the SDN controller at all costs.

In the technology industry, hype is a constant. This is no different with the up-and-coming technology of software-defined networks. In this case, however, the hype is justified: SDN could change the network security landscape as we know it.

Over the past couple of years, software-defined networking (SDN) has developed from merely an idea to a paradigm that large networking vendors are not only embracing, but also talking up as their model for future enterprise network management. This technology adds greater granularity, dynamics and manageability to networking, but brings up other concerns that should be seen from a security perspective.

In this tip, we'll explain what SDN is and explore the network security pros and cons that enterprise networking and security pros need to know.

A definition of software-defined networking

To understand a few of the security benefits and downfalls of software-defined networking, let's take a quick tour of the technology. Software-defined networking is the ability to split the data plane from the control plane in routers and switches. The control plane, which has historically been proprietary and known only to the vendors that developed them, would be open and controlled centrally with SDN while having commands and logic sent back down to the data planes of the hardware (routers or switches).

This provides a view of the entire network and affords the ability to make changes centrally without a device-centric configuration on each router or switch. The ability to manage the control planes through open protocols such as the OpenFlow standard allows for precise changes to networks or devices that will increase the speed and security of the network.

SDN security benefits

Like everything else, there will be both benefits and concerns when implementing new technology. Let's review some of the benefits of software-defined networking:

  • By having the free-moving network of SDN, engineers are able to change the rules by having a quick, high-level view into all areas of the network and being able to modify the network.
  • This freedom and control also allows for better security of your systems. By having the ability to quickly limit and see inside the network from a centralized viewpoint, managers can make changes with efficiency. For example, if there were a malware outbreak within your network, with SDN and OpenFlow you'd be able to quickly limit the outbreak from one centralized control plane that would stop the traffic without having to access multiple routers or switches.
  • Being able to quickly change things in the network enables managers to perform traffic shaping and QoS of packets in a more secure matter. This ability exists now, but the speed and efficiency doesn't exist and will limit the manager's ability when attempting to secure the network.

SDN security concerns

With innovative new technology come security concerns that could easily go overlooked. Let's take a look at a few security-related issues to be aware of when implementing SDN. The majority of software-defined networking security concerns are going to evolve around the controller itself. The controller can be considered the brains of the switching/routing, which allows the control panel from each system to be centrally managed.

The largest SDN challenge for security managers is securing the controller at all costs.

The largest SDN challenge for security managers is securing the controller at all costs. Now that the brains have been taken out of the routers or switches and replaced with the new controller, this device needs to be hardened and secured through the following steps:

  • Knowing and auditing who has access to the controller and where it resides on the network is a big security concern. It's important to remember that access to the controller could potentially give complete control to an attacker, so it's vital that it is secured.
  • Verify the security between the controller and end nodes (routers or switches) -- specifically that they're communicating over SSL to prevent any malicious intent from accessing the controller. As with anything else, if security isn't baked in from the start, it must be added later on, and it's always more difficult and expensive to do it that way. Make sure the security between the node and controller is configured properly.
  • Verify that there is high availability in the controllers. Creating a business continuity effort for controllers is important because if they are lost, the ability to manage the network is also lost -- and consequently, so are all the benefits of SDN and OpenFlow.
  • Verify that everything that comes out of the system is logged. Since managers have control over the network centrally, log every change made and send it to the company's log management solution.
  • When implementing SDN, verify that the organization's SIEM, IPS and any other filtering technology that might block or log changes is updated accordingly. Correlate the logs from the SIEM to alert the manager of changes. Tracking custom events with the SIEM on the control, like login failures and policy changes, will assist with the security of the system.
  • Verify that the IPS isn't identifying any of this traffic as malicious. Configure the appropriate rules in the filtering systems to allow the controller to speak with the nodes when needed.

In conclusion, software-defined networking is an emerging technology that can allow for granular security by giving an administrator a complete view of the enterprise network. However, by giving the SDN controller centralized management over network nodes to push down changes to these systems, it becomes imperative that the security around this system is locked down. This system is the brains of SDN, and without proper security wrapped around it, the network becomes completely vulnerable to malicious attacks or accidental changes, both of which can take a network down. Now is the time for organizations to ensure that security is a primary consideration in the design, deployment and management of SDNs.

More on software-defined networking

  • Software-defined network makes cloud management easier for providers
  • software-defined networking architecture: The application tier

About the author:
Matthew Pascucci is senior information security engineer at a large retail company where he leads the threat and vulnerability management program. He has written for various information security publications and spoken for many industry companies, and is heavily involved with his local InfraGard chapter. You can follow him on Twitter @matthewpascucci or check out his blog at www.frontlinesentinel.com.

Next Steps

Addressing SDN security issues by securing the controller.

This was last published in October 2012

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