5 terms you need to know before you employ VoIP

Make sure you are familiar with these five terms before deploying VoIP.

This page is a part of SearchSecurity.com's learning guide,
Secure VoIP tutorial: Understanding VoIP security best practices.

Before beginning a successful VoIP rollout across your organization, you need to be familiar with the following five terms:

1. Network Address Translation

Make sure your network and security infrastructure, including firewalls, IDSVPNs, etc., are voice-optimized and capable of supporting the advanced security requirements for VoIP. Traditional static policy rules are not adequate for VoIP traffic control. The protocols involved dynamically allocated ports during call setup, requiring opening and closing of ports at the security gateway on demand. Inspection of VoIP traffic not only at the network layer, but also at the application level is necessary to deal with the challenges of VoIP protocols in Network Address Translation(NAT) environments. Finally, bandwidthlatency and quality of service become critical requirements for network and security infrastructure, when processing multiple simultaneous voice streams.


Critical security vulnerabilities are being identified on a regular basis, leaving systems vulnerable for denial of service and even more severe buffer overflow attacks. As your IP PBX is at the core of your VoIP infrastructure, ensure that the base operating system of your IP PBX, as well as network infrastructure, are always updated and patched for the latest security vulnerabilities. Regular security assessments of your VoIP infrastructure provide identification and remediation of such security flaws to avoid attacks and prevent outages.

3. VoIP phone

Always properly secure any remote access and configuration capabilities to individual VoIP devices to eliminate any backdoors. VoIP phones as the endpoints are the most common and widest accessible component of a VoIP infrastructure. Default login and administrator passwords on such devices are a very common avenue for attacks. Disable any insecure remote access features, such as FTP and Telnet, and disable local administration and management features.

4. IPsec

If your VoIP traffic goes over unsecured channels, such as the Internet, use encryption technologies like IPsec tunnels to secure the VoIP traffic. While many of the VoIP protocols include capabilities for encryption and authentication, most of them are optional. It is essential to establish secure tunnels for carrying the VoIP information streams (call signalingcall control and media) between sites and over untrusted networks.


Structure your network and leverage VLANs to separate voice and data devices and traffic. While this may have limited impact on security, deploying VoIP devices on separate VLANs permits isolating data traffic from voice and signaling traffic, as well as utilizing Quality of Service (QoS) capabilities.

By Gerhard Eschelbeck
20 Dec 2004 | SearchSecurity.com

This was last published in September 2004

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What are the advantages of deploying VoIP?