For many, the cost of hacking isn't so clear. This is, perhaps, the reason why a lot are still taking security for granted even with increasing reports of VoIP attacks.

Just how do hackers make money from compromised VoIP accounts? A report by Current.com.au provides a very good glimpse of their operations.

According to the Australian online magazine, cyber criminals earn millions of dollars by making international calls to premium numbers -- often their own. They gain entry into their victims' accounts because many of them don't bother to change default access PINs and passwords.

The report did not state how much have been made by hackers worldwide, but if one considers a small sample of scammed networks in the United Kingdom, South Africa and Romania where 11 million minutes of illegal calls worth over US$1 million were made in 2010, the figure could amount to several million dollars. You can read the full report here.