http://news.bbc.co.uk/2/hi/technology/4259554.stm

The biannual Symantec Threat Report identified Voice over IP (Voip) systems as a technology starting to interest hi-tech criminals.

The report predicted that within 18 months, Voip will start to be used as a "significant" attack vector.
"While there are currently very few reported attacks directed at Voip systems," he said, "Symantec believes it's only a matter of time before attackers target it more intensely."

The report also said that Voip could fuel a renaissance of an old hacking technique known as war-dialling.

In its original form this involved making a huge number of phone calls to find out which ones respond with a data tone.


With the VoIM also being release by Yahoo and others just another method of attack/spamming.