As criminal gangs get involved, the 'independents' that currently dominate the spam and virus market will be squeezed out, reducing the total number of attacks.

Eugene Kaspersky, head of antivirus research and co-founder of Kaspersky, warned the latest MiMail worms were the first in a new type of attack aimed at deriving financial profit from viruses and malware.

Recent MiMail variants collected and forwarded PayPal account details to the worms' creators.

'The business of the mafia is business, and there could be a lot of money to be made from malware and spamming. As they consolidate control, the business of hacking and virus writing they will squeeze out independents. Spam will be an early target,' he said.

And he added: 'If you are a spammer or malware developer, sooner or later the mafia will come knocking on your door.'

Kasperksy said although overall virus attacks might decline, targeted viruses could be used to steal commercial valuable secrets or bring down networks.

To combat these threats a new set of internet protocols would need to be designed with security in mind, he said.

'Spam is ripe for organised crime, as the majority of spam relates to the vice and drugs industry,' said Professor Neil Barrett, technical director at Information Risk Management.

'The only downside to that is that spam isn't that effective as a marketing tactic so may not be a money-spinner. I'm not sure I agree on viruses, since they are untargeted and not very efficient.

'But the capability to launch denial of service attacks for extortion fits perfectly with the mafia business model.'