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Viruses Call Up Your Cell Phone

Danger level: Medium | Likelihood: Low (USA), medium (Europe and Asia) | Target: Cell phone and smartphone users

As if viruses on your PC weren't bad enough, these nasty programs now target your cell phone. Like their computer-based cousins, some mobile viruses wreak havoc by crashing the phone and wrecking its operating system. Others are mere nuisances that change icons and make the device more difficult to use.

And of course, some are strictly money-minded. A Trojan horse currently infecting Russian phones sends text messages to services that charge the sender a fee.

So far these pests aren't a major problem in the United States, but they are significant threats in Europe and Asia. And a lot of experts think it's just a matter of time before the money-grubbing aggravations arrive on American phones.

Like many real-world biological agents, a cell phone virus typically needs to be physically close to another susceptible phone to make the leap. Computer security experts like Mikko Hyppönen, chief research officer for Finnish antivirus firm F-Secure, often use unsecured phones as bait to see what slithers in. On one London trip, Hyppönen's phone got hit four times via Bluetooth, which has a maximum range of about 30 feet. Bluetooth is the most common--but not the only--vector of infection. The Mabir virus, for example, spreads via SMS messages.

The vast majority of mobile viruses hit phones using the Symbian operating system, but a few go after Windows Mobile- and Java-based phones. Following the discovery of Cabir.A in June 2004, the number of viruses has continued to climb. There were 211 variants as of May 15, 2006, up from 156 at the end of 2005.