Cellular phone viruses are still mercifully rare, but more than 60 percent of global companies mention security concerns as a reason for not giving employees advanced handsets, a survey found on Tuesday.

Of 240 companies polled specifically about the threat of viruses, 82 percent of businesses expect a cellular network to be more at risk than a fixed-line network, but only a quarter have assessed the real threat that comes from their staff's handsets, the Economist Intelligence Unit found.

"They may be erring on the side of caution," said Ollie Whitehouse, a wireless research scientist at anti-virus and security software vendor Symantec (SYMC), which commissioned the study.

There are currently about 100 cellular viruses that can disable a phone or create bills of hundreds of dollars by sending pricey picture messages. The very first cellular virus spreading "in the wild" emerged less than two years ago.

While this is still a tiny number compared with personal computer viruses, the threat is expected to increase.

"There's no technological reason we won't see the same level of attacks as we've seen with desktop and laptop computers," Whitehouse said.

Advanced cellular phones run the same kind of applications as desktop and laptop computers, and they have multiple wireless connections to get infected and spread a virus, he added.

Research group Gartner predicts that wireless e-mail users worldwide will reach 20 million in 2006 and 100 million in 2009.

The Economist study, published ahead of the CTIA wireless trade show in Las Vegas, showed that over 80 percent of the companies had a security policy in place for laptop computers.

Research firm IDC believes the market for cellular security software will grow about 70 percent a year to nearly $1 billion in 2008.

One of the reasons for the relatively slow spread of cellular phone viruses so far has been the greater variety of operating systems running cellular phones compared with computers, which mostly run on Microsoft's (MSFT) Windows operating system.

Consequently, to target a large number of cellular phones, writers of virus software have to put in a lot more work.