The Essential Guide to VoIP Privacy

Updated: April 30, 2009

People generally assume that their private phone calls are just that: private . VoIP users, however, shouldn't take privacy for granted.

The problem with most VoIP calls is that they travel over the Internet, a very public network. This means that calls are vulnerable to snooping at various points throughout their journey. And even private-network VoIP calls can be tapped if access can be gained to the physical wiring. As a result, business competitors, employees, criminal gangs, tech hobbyists and just plain snoops can all listen in to a business's outgoing and incoming VoIP calls. All that's needed is a packet-sniffing program , easily downloaded from the Internet, and perhaps a tiny piece of hardware to tap into a physical wire undetectably.

But the news isn't all bad. Methods and systems are available to safeguard VoIP traffic. And while VoIP is susceptible to digital eavesdroppers, the technology also commonly provides an array of built-in features that can actually enhance users' privacy.

Protection Measures

VoIP calls are vulnerable to interception at two stages: the call setup and the call data flow. Tapping into the call setup provides the intruder with information on who called a particular number, something that may be of interest to a competitor, employee or spouse. Monitoring the call data flow allows the intruder to actually listen to the call as it is taking place.

Security installed on network perimeter devices, such as routers and gateways , can protect VoIP-call confidentiality by encrypting both the call setup traffic and the audio stream using technologies such as TLS (Transport Layer Security), ZRTP (Z Real-Time Transport Protocol), SRTP (Secure Real-Time Transport Protocol) and IPSec (IP security). Meanwhile, businesses using a VPN (virtual private network) can utilize the technology's built-in encryption for gateway-to-gateway VoIP-call protection. This security is automatically supplied to all VoIP users - even traveling employees connecting to the VPN from a laptop. Internal VoIP security can be bolstered by running the technology on the enterprise network , allowing the infrastructure's usual safeguards to keep calls safe from internal snoops.

Businesses and individuals subscribing to a hosted-VoIP service can take advantage of the encryption many providers have incorporated into their software. Skype Ltd. , for example, has added encryption support into its proprietary client software.

There is a growing awareness of the issue and VoIP encryption tools are becoming available, most notably Zfone - the encrypted VoIP project created by Phil Zimmermann, the inventor of the leading general encryption solution, PGP .

Privacy Support

Although unprotected VoIP calls are vulnerable to various types of snoops, VoIP itself can help users maintain their privacy. Various IP-based features allow users to isolate themselves from unwanted callers, making it much more difficult for these individuals to intrude into daily life.

  • Anonymous-call rejection: This feature allows users to reject incoming calls from people who have blocked their phone number and name. The capability effectively screens out telemarketers, cranks and other individuals who wish to hide their identifies.
  • Outbound-caller ID blocking: By stopping the transmission of caller-ID data, the user can hide his or her identity (although that also raises the possibility of having the call blocked at its destination by anonymous call-rejection).
  • Call blocking: This feature enables users to screen calls from specific phone numbers.
  • Selective call forwarding: By forwarding specified incoming calls to other destinations (such as an office or home line), the user can keep certain types of calls from disrupting business or family activities.
  • Selective call acceptance and rejection: This feature lets users accept or reject certain incoming calls depending on specified criteria.
  • Do not disturb: By directing all incoming calls to voice mail without ringing the phone, users can steer clear of incoming calls without potentially missing important news.
  • Extra lines: Many VoIP services allow customers to purchase additional lines at reduced rates. Such auxiliary lines allow users to tier their phone service in a way that reserves one number for close personal and business contacts and then dedicates one or more other lines for various types of causal acquaintances.
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