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Cisco IP Telephony Security Framework

  • Sample Chapter is provided courtesy of Cisco Press.
  • Date: Sep 21, 2012.

Chapter Description

This chapter examines the Cisco IP Telephony Security life cycle. It also shows how to develop an IP telephony security policy, evaluate cost versus risk, determine the level of security required for your IP Telephony network, and develop Cisco IP Telephony Security Framework.

The threats, the remediation, IP Telephony Security methodology and much more has been discussed in previous chapters. However, the objective has always been to amalgamate IP Telephony and conventional data services onto a shared network infrastructure, without compromising the security of either service. The intention has been to apply protective mechanisms against all types of attacks that must be applied in a holistic manner throughout the enterprise network. The two main principles of an IP Telephony Security Framework are the simplification of design and configuration, and the limitation of exposure.

It is time to start putting together your IP Telephony network security strategy together. With the basics of what makes your secure IP Telephony network out of the ordinary, it is time to move on and choose the best style of security network to suit your needs. In many ways, this can be a subjective process because you might prefer one type of network security rather than another regardless of objective criteria. There’s nothing wrong with taking that approach as long as you’re armed with the facts, and that’s what this chapter is all about.

This chapter covers the following topics:

  • Cisco IP Telephony Security life cycle
  • Develop an IP Telephony Security policy
  • Evaluate cost versus risk
  • Determine the level of security required for your IP Telephony network
  • Develop Cisco IP Telephony Security Framework

Cisco IP Telephony Security Life Cycle

Cisco understands and values the importance of network security and continuously drives toward building robust, scalable, and secure products, and networks. It is vital that security is induced in design wherever possible (rather than implemented post-deployment of the network). The process of developing and securing your IP Telephony network should follow what is popularly known as a security wheel. After developing an IP Telephony Security policy, you can secure your IP Telephony network. (An IP Telephony Security policy acts as a guide for implementing various security measures without which the IP Telephony network security will neither be complete nor based on the ethics and principles of your organization.)

The security wheel, as shown in Figure 4-1, projects the verity that IP Telephony network security is a continuous process built around your corporate security policy.

Figure 4-1

Figure 4-1. Cisco Security Wheel

After the IP Telephony network is secured, it should be monitored for any deviations from normal behavior, for example, abnormal usage of services, network and application level attacks, illicit scans, and log analysis to ensure that it stays secure.

After the monitoring phase comes the testing phase. Testing can be done by an organization, or it can be outsourced to a third-party, such as the Cisco Advanced Services. Network and IP Telephony administrators and engineers should use the information from the monitoring and testing phase to make improvements to the security implementation. They should also adjust the IP Telephony Security policy as new vulnerabilities and risks are identified.

For more details on the security services offered by Cisco Advance Services and other security groups within Cisco, visit http://www.cisco.com/en/US/products/svcs/ps2961/ps2952/serv_group_home.html.

Enabling IP Telephony Security

Implementing and enabling IP Telephony Security is neither a single step nor a one-time process. It is a constant and continually improving cycle, which must be reiterated time and again as and when new threats evolve or new requirements need to be addressed. Figure 4-2 illustrates the IP Telephony Security cycle and its various phases.

Figure 4-2

Figure 4-2. IP Telephony Security Life Cycle

At the core, this cycle is based on the Cisco security wheel; however, it is more detailed and explicit toward the IP Telephony network security process.

Security and Risk Assessment

The process begins at security and risk assessment; during this stage any new or existing vulnerabilities and security loopholes are discovered. During this phase, a rigorous process consisting of multiple objectives is carried out. These include however not limited to the following:

  • Evaluating and identifying the principle assets
  • Identifying any existing security concerns
  • Exploring any possible new threats or attack vectors
  • Evaluating the cost of security

The security assessment of the enterprise IP Telephony network infrastructure helps support key business processes. The IP Telephony Security assessment should cover the following elements of your IP Telephony environment:

  • Network devices (routers and switches) vulnerabilities
  • Network and security services (firewall, routing protocols, and anti-spoofing services)
  • Network access layer, where endpoints connect to the network, and the distribution and core layers of the internal network
  • IP Telephony services, endpoints, and applications, such as Presence, IP Phones, Call Control, gateways, and so on

The objective of security assessment is to identify potential weaknesses in your IP Telephony network, which may lead to toll fraud, denial-of-service (DoS), eavesdropping on voice calls, and unauthorized access to voice mail systems within your IP Telephony environment. The result is a report on the network security posture, including recommendations for network infrastructure and IP Telephony application security improvements.

Risk assessment helps identify the vital assets of your IP Telephony network and evaluate the potential cost of security. The topic of risk assessment is covered in detail in the section “Risk assessment.” The completion of the risk assessment phase triggers the next phase, in which IP Telephony Security policy (strategy) is developed.

IP Telephony Security Policy Development and Enforcement

The process of development and enforcement of IP Telephony Security policy is base-lined on corporate security policy and objectives. An IP Telephony Security policy is much like a network security policy. However, the major difference is that the IP Telephony Security policy is explicitly developed for IP Telephony network covering the network, applications, and services relevant to IP Telephony infrastructure and services. You must recognize that the development of an IP Telephony Security policy is not a lone effort by the IP Telephony team. Instead, it should be done in collaboration with the network and security teams to ensure that all aspects and view points are covered as they pertain to IP Telephony Security.

Planning and Designing

The subsequent phase is the planning and designing phase, in which you plan and design the blueprint for deployment of your IP Telephony network. As a best practice, it is in this phase that you should integrate security with the design being developed instead of deploying security after your IP Telephony network has been deployed. The design should be such that the IP Telephony network and the services based on it are scalable, robust, supple, and most obviously, secure. The planning for deployment should include security as the integral component and should be done in such a manner that a layered security approach is adopted instead of concentrating security at one point, for example, at enterprise perimeter.

IP Telephony Network and Application Security Deployment

This is the phase where maximum action can be expected. It goes right from deploying and enabling security on IP Telephony applications (Call Manager and Unity Connection) on servers to IP Telephony network (access layer switches, routers) to IP Telephony endpoints. As mentioned earlier, if security is planned into the design, it becomes much easier to implement in coherence with the underlying functional network. In other words, implementing security for IP Telephony network becomes seamless.

IP Telephony network security can be organized into the following categories:

  • Hardware and device security (endpoints and servers)
  • Network security (Layers 2 and 3 and upper layers)
  • Application security (Call Control, voice messaging, presence, and so on)
  • Management and monitoring (SSH and logging)

Operate and Manage

In this penultimate phase, you leverage the services offered by your IP Telephony network. It is time to reap the benefits of your hard work! Your IP Telephony network is fully operational, and you could bring it into production. However, it is also time to ensure that things go the way they were planned and that there are minimal hiccups from the intended operational and management perspective. Ensure that proper administrative and other privileges are assigned to the intended authorized staff. Furthermore, ensure that only the legitimate users can leverage the IP Telephony services without any loss of service or disruption in the IP Telephony environment. This phase almost amalgamates with the last phase, that is, monitor the IP Telephony network.


At this point, your IP Telephony network should be under ideal conditions fully functional, and to ensure that it remains that way, you must consistently keep an eye on the health of your IP Telephony network. IP Telephony monitoring tools, techniques, security, and best practices are discussed in Chapter 16, “Cisco IP Telephony: Network Management Security.” Monitoring and responding to potential threats is a manifold process and requires monitoring and reporting any ‘deviations’. Now, let’s consider the scope of word deviation in perspective of IP Telephony network management and monitoring. Deviation could be described on one hand as the anomaly induced by improper or unjustified use of the services provided by your IP Telephony network. On the other hand it can be described as the threats that have matured and cause the loss of integrity, confidentiality, and availability of your IP Telephony network. Thus, it becomes paramount to have proper monitoring mechanisms in place and have these deviations reported as soon as they are discovered so that they can be dealt with either via an automatic defense system (for example, Firewall, Network IPS, or Host IPS) or manually.

2. Developing an IP Telephony Security Policy | Next Section

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