IP telephony poses special security sensitivities.
Why are people so concerned about IP telephony security?
It's a historical thing. Ten years ago, the wireless industry in the USA used analog cellular systems to connect millions of subscribers. Every communication was vulnerable to eavesdropping with the simplest of radio scanners and it was a great technological entertainment before the Internet hit the scenes. The dark side of analog was toll fraud. In 1995, toll fraud was a $700 million problem for the wireless industry. Users would simply have their phones on in a major metro area, where these devices would broadcast their identity for thieves to capture. Once captured, they'd 'spoof' the cell phone and wrack up thousands of dollars in long distance calls to countries around the world.
In fact, I declined wireless service until digital was available.
It's a personal thing. Imagine the pain and suffering that could be caused if your phone conversations were played back on the news. Or were printed in the newspaper. Would jokes be taken out of context? Things mis-represented? Our communications are not always as Politically Correct and as innocent as we'd like them to be. Ask the folks who monitor the FBI wiretaps or the NSA which records and analyzes every phone conversation entering or leaving the US. It is a nasty business.
The question of FBI monitoring is really only an issue in public and in what I distinguish as the VOIP industry. VOIP is about consumers and regulatory bypass. IP Telephony, on the other hand, is for enterprises and higher productivity.
The FBI needs to monitor VOIP (consumer) communications and this can be difficult using the classic 'tap at the Central Office' model, since the flow of packets can be so easily mixed with so many communications by the time it arrives at the CO. And making it virtually impossible to generate a clean audio stream without serious computing enhancement which might be considered as tampering with evidence. They also need to assure the judge issuing the wiretap warrant that they are monitoring your conversations, but not your neighbors.
Next, we'll get to the security of IP Telephony.