Experts are predicting that the boom in VoIP services, such as Skype, is going to bring with it a new kind of cyber crime.

Newport Networks, which makes VoIP equipment, has published worrying research, which shows that cyber criminals are already targeting people who use internet phone services.

And, in fact, usernames and passwords from VoIP accounts are selling online for more than stolen credit cards.

Credit card details can be bought for around £6 each, while VoIP account details fetch about £9.

Once someone gets hold of these two key pieces of information, they can use the telephone service for free, while the victim builds up massive charges.

Dave Gladwin, vice president of products at Newport Networks, told the BBC: "It [this type of crime] is still at an embryonic stage but as voice adoption increases it becomes more of a problem and needs addressing".

The firm adds that there are also problems with criminals overlistening on phone calls.

Gladwin adds that security is more of an issue for home VoIP users as public or home Wi-Fi networks are often unsecured.

In fact, he claims, "90% of carriers don't offer a secure VoIP service", [which doesn't include Skype] and it would cost around £2/£3 per subscriber to bump security levels up.