Securing VoIP networks

Safe Call

© mipan, Fotolia

© mipan, Fotolia

Article from Issue 99/2009
Author(s): , Author(s):

Eavesdropping on conversations on a LAN is easier than ever thanks to insecure VoIP installations. You don't need to bug restaurant booths or tap phone lines – standard Linux tools are all a hacker needs.

Many small to mid-sized enterprises simply connect their new VoIP systems to existing LANs. Road warriors call in via the Internet, and remote branches use a standard connection to reach the mother ship. Unfortunately, this kind of installation doesn't provide anything in the line of VoIP infrastructure security.

In this article, we look at some of the special concerns affecting VoIP and describe some strategies and optional protocols for protecting voice communications.

A Typical VoIP Connection

Session Initiation Protocol (SIP, RFC 3261) [1] is the most popular open VoIP standard for initiating, negotiating, and managing VoIP connections. In combination with Session Description Protocol (SDP, RFC 4566) [2], which handles audio or video codec negotiation, SIP transmits information about the connection between the calling parties. Once the connection is established, the parties send and receive data using the Realtime Transport Protocol (RTP) [3].

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