This year, the Russian antivirus company Kaspersky Lab reported on a new malicious program that stole money by taking over Nokia phones and making small charges to the owners’ wireless accounts. Last month, an Australian student created an experimental worm that hopscotched across "jailbroken" iPhones, which are phones altered to run software Apple has not authorized. The mischievous worm did not cause any damage; it just installed a photo of the '80s pop star Rick Astley. But to security experts, it suggested that pernicious attacks on iPhones are possible.

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This year, Lookout began testing security software for phones running the Windows Mobile and Android operating systems, and it will soon introduce security applications for the BlackBerry and iPhone. The software protects phones against rogue programs and gives phone owners the ability to remotely back up and erase the data on their phones. It also lets them track the location of their handset on the Web. A basic version of the software is free, while the company plans to charge a monthly subscription for a version with more features.

"It feels a lot like it did in 1999 in desktop security," said John Hering, Lookout's 26-year-old chief executive, who for years has done research demonstrating security vulnerabilities in phones. "People are using the mobile Web and downloading applications more than ever before, and there are threats that come with that."