According to McAfee Labs, VoIP vulnerabilities have increased dramatically in recent years, from fewer than 20 vulnerabilities in VoIP products in 2006 to almost 60 in 2009.

"Cisco equipment was by far the biggest source of VoIP vulnerabilities, outpacing competitors Nortel and Avaya by a factor of five, the report found," according to Infosecurity.

"Some... exploits can be used to support attacks such as voice phishing (vishing), in which spoof calls are made from criminals pretending to be employees of legitimate organizations trying to 'confirm' information about the victim," the article states.

Click here to read the Infosecurity article.