The rising popularity of smartphones such as the BlackBerry and the iPhone will make them targets for viruses and spam, security experts believe.

In the past few years the internet has experienced a huge rise in security problems, led by criminal gangs who have used spam and viruses for financial scams. Mobile phones have remained relatively unscathed, but that is set to change as sales of smartphones surge.

In the first three months of this year 32.2 million smartphones were sold - 11 per cent of all handset sales and a 29 per cent increase on the same period last year.

These e-mail and internet-enabled handsets are moving out of the corporate market into consumers' hands, and the recent launch of the 3G iPhone is expected to fuel sales further. Credit Suisse analysts predict that 275 million smartphones will be sold next year, boosting penetration to 19 per cent and making the mobile world attractive to criminals.

Neil Cook, vice-president of technology services for Cloudmark, a messaging security company, estimates that penetration of smartphones needs to reach 20 per cent to 30 per cent before it becomes worthwhile for hackers to spread viruses. Spam is a problem in India and China, and North America and Europe are expected to follow.

Mr Cook said that the rise in spamming and scams boils down to economics. “Spammers are really very good businessmen,” he said. “They see new opportunities and new markets. As new media becomes attractive to spammers, they move in there. They will move anywhere if they can make a return on investment.”

Another attraction for spammers is that mobiles are quickly outgrowing the number of computers. Gartner, the industry analyst, forecasts that there will be four billion mobiles compared with 1.3 billion computers by 2010. Mobile spam is rampant in China, where it is much cheaper to send texts and fewer people have computers, Mr Cook said. Others are more sceptical. Sending 100,000 spam e-mails costs only a few dollars, which is significantly cheaper than texting, Carole Theriault, senior security consultant for Sophos, a computer security company, said.

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