A proof of concept program has been developed and demonstrated that allows significant and possibly large-scale exploitation of Session Initiation Protocol (SIP), permitting an individual to tap into corporate VoIP networks. The exploit could also be done at the ISP level, permitting an intruder to eavesdrop on large numbers of VoIP calls, perhaps simultaneously.

This is an extremely dangerous development, one that I have feared could happen once telephony networks are converted to TCP/IP. This is a classic example of technology being developed and implemented without adequate consideration for security and privacy. Other examples of technologies whose early editions were too weak for prime time: WiFi networks, analog cellular networks (remember the clone wars?), e-mail (spam and spoofing are still significant problems), domain name service (significant weaknesses abound), FTP, Telnet… shall I go on?

Organizations that utilize VoIP and SIP trunks to branch offices or service providers need to consider protecting these communications with VPN technology. SIP’s security features alone cannot be relied upon to protect VoIP traffic.

Article here:

http://www.techworld.com/security/news/index.cfm?newsid=10736

More on the risks of new technologies here.

How to protect corporate VoIP networks here.