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Wireless IP telephony heightens security concerns

Take a look around at what's happening with IP telephony these days, and you'll quickly learn a new definition for an old buzzword—namely, convergence. Whereas it used to mean the inevitable overlapping of voice and data communications (and probably still does, once I remove tongue from cheek), to me it looks like it now refers to the simultaneous use of Wi-Fi (

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802.11x) technologies with equally wireless IP telephone handsets. If laptops and PDAs can go mobile inside a broadcast radius, why not enable the same capabilities for wireless IP telephones as well?

Why not, indeed? But consider further that Wi-Fi has its own well-known set of security problems and emerging solutions, and that the Session Initiation Protocol (SIP) so often used in IP telephony has its own security problems as well. In this case, some experts suggest that the combination of the two may be less secure than either one on its own, so that here the sum may be even less secure than the individual parts.

In fact, according to a recent expose from Jim Louderback in eWeek, the following kinds of security issues are reasonably likely to occur in IP telephony installations, where exposure increases when IP phones go wireless:

  • Because most VoIP traffic is unencrypted, anybody with network access can listen in on conversations with a little effort and some readily available session monitoring tools.
  • Attackers can spoof SIP and IP addresses, then hijack ongoing conversations. This gets really scary if people think they're talking to legitimate telesales operators and place orders, only to learn their credit card info has wound up in the wrong hands, with unwanted results.
  • Denial of service is also easy to foment, should floods of bogus SIP requests arrive at a server, or large file transfers be initiated to numerous phones at the same time (and alas, the same kinds of techniques can permit transfer of unwanted voicemail to any or all IP phones, or constant ringing with nobody on the other end of the call).

Other experts point out that these kinds of exposures are part of what it means to use the Internet as a telephony infrastructure, but that well-managed, secure private networks are not subject to the same risks. Likewise, many IP telephony providers are routinely using encryption, secure session protocols, and incorporating strong authentication services to prevent hijacking or eavesdropping.

But as the networking world learned once the initial rush of enthusiasm for wireless data networking wore off, broadcasting data brings with it a whole new collection of security issues and requires strong, thoughtful designs and implementations to maintain a proper level of security. We still have a lot to learn, and many designs to refine and improve, before IP telephony achieves rock-solid safety and security as well.


Ed Tittel is a regular contributor to numerous TechTarget Web sites, and the author of over 100 books on a wide range of computing subjects from markup languages to information security. He's also a contributing editor for Certification Magazine, and series editor for Que Publising's Exam Cram 2 series of cert prep books. He was recently awarded the NPA Career Achievement Award at Network+Interop 2004. E-mail Ed at etittel@techtarget.com.


This was first published in May 2004

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