2007 is apparently the year for attacks on IP telephony systems.
With the number of business IP phones sold expected to grow from 9.9 million in 2006 to 45.8 million in 2010, Security vendor, Symantec speculates that VoIP networks will become a new vector in phishing attacks.
Voice phishing or 'vishing' attacks leverage voice-over-IP. As a result, such attacks can be conducted cheaply enough that phishers might see a sufficient return on their investment. The Register reports that "Other security vendors are fretting over the possibility that VoIP networks might be used to spread malicious code. Rather than using the IM clients' built-in VoIP software packages, such as Skype, hackers might design code that changes the numbers associated with users' banks to phone lines controlled by hackers."