Viruses on mobile phones are still rare, but their number has been growing quickly, as handsets increasingly resemble small computers that connect with one another and the Internet, industry officials said.
Companies making antivirus software for mobile phones said at the 3GSM World Congress, a conference taking place in Cannes, France, that they saw a sharp rise in interest from carriers after at least six new viruses for mobile phones emerged last year.
The six basic viruses have already proliferated into some 30 different variants, as source code for them has been published, on the Internet, said Antti Vihavainen, head of mobile antivirus unit at software company F-Secure.
This has made operators start to pay attention.
The Nordic region's biggest telecoms operator, TeliaSonera, said it was already monitoring the release of mobile viruses, even though they're not yet a problem.
"There is no reason to panic, but fasten your seatbelt," said Hakan Dahlstrom, who's in charge of the carrier's Swedish mobile networks.
F-Secure has agreements to provide antivirus protection for Finland's second-biggest carrier, Elisa, and for Swisscom. The recommended retail price for users who want to download the product is $2.61 (2 euros) per month.
"Previously, it had been a little like selling refrigerators to Eskimos," Vihavainen said about attempts to sell the software to mobile operators. "Now we are actually getting calls from major operators asking us what to do."
Victor Kouznetsov, senior vice president for mobile security solutions at McAfee, which protects the phones of Japanese operator NTT DoCoMo, said: "Over the last three to four months, I was home three weeks. That tells you a lot about the level of interest and demand out there."
"People are asking what can we do today," he added, "and what kind of plans can we develop for tomorrow. A lot of people want to develop plans for it before it explodes on them."
Today's 30-virus total for mobile phones is a tiny number compared with the more than 112,000 known viruses that invade personal computers, but industry experts say that the number will increase quickly because the mobile handset is likely to become the most common way of accessing the Internet in a few years.
The increased activity from mobile virus writers comes as the number of advanced phones, which can connect with networks and each other and install applications, approaches critical mass, some experts said.
It also coincides with the release of new security measures for the Windows XP operating system for personal computers by the world's biggest software company, Microsoft. The new level of security may have led some of the PC virus writers to turn their efforts to phones, Vihavainen said.
Last year's viruses were designed more to prove infection was possible rather than to really damage phones. They made themselves immediately visible to the user, such as by changing all icons on the screen to skulls, and some needed the consent of the mobile device owner to install themselves.
But experts said the really dangerous ones would stay hidden, possibly sending text messages to other phones, making costly calls to special numbers, spamming all contacts in the phone's address book or stealing passwords.
"There are definitely viruses now out there, but their spread is still very limited," said Raimund Genes, head of European operations at Trend Micro, an antivirus company.
"I think that when we have a real outbreak, it will be one with a commercial interest," he said.
Four of the six basic virus types so far have been written for the Symbian operating system and two for Microsoft-powered devices. There are about 20 million phones with the Symbian system in operation now, versus the total 1.7 billion mobile phone users last year.
Experts said Symbian was more targeted than others because it was emerging as a leader in operating systems for advanced phones able to surf the Internet and make wireless connections with other phones via Bluetooth. Virus writers always target the biggest system, experts said.