Authentication -- anything from allowing access only from phones with known MAC (media access control) addresses, to personal IDs, passwords, and PINs -- can prevent someone from placing a rogue phone on the network. Also consider using static IP addresses for your IP phones, mapped to MAC (media access control) addresses. And, of course, keep up to date with the latest security patches on all your voice mail and call-processing servers and make sure you have good virus protection. Who knows? Your extra efforts on behalf of IP telephony may have a welcome spinoff effect and increase the reliability of your network overall.

Leon Erlanger is a freelance author and consultant specializing in security.