Symantec, McAfee, and a swarm of rival security software makers are beginning to ship a wider number of products designed specifically to protect smartphones, the more PC-like handhelds that are finding their way into a growing number of enterprises.

Sales of smartphones grew by roughly 66 percent to 81 million units in 2006, according to estimates published by researchers Gartner, in Stamford, Conn.

And while the devices haven't yet penetrated the United States market to the same extent they've found homes with business users in areas of Asia and Europe, market watchers are predicting that a vast majority of large U.S. companies will distribute at least a handful of the handhelds to workers before the end of 2007. Many will buy hundreds.

Based on the growing proliferation and complexity of smartphones -- which offer wireless e-mail, Internet access, and mobile business applications along with their calling functions -- security applications vendors see range of opportunities to carry the same tools they've been selling on the desktop onto the emerging mobile platforms.

On March 26, Symantec launched its new set of security applications for smartphones running on Microsoft's Windows Mobile operating system.

In addition to adding Microsoft's flagship device OS to its stable, which also includes coverage for high-end handhelds based on software made by Palm and Symbian, the package introduces new VPN (virtual private network), data encryption, anti-spam features.

Symantec and its rivals are betting that companies will soon want to license robust suites of mobile security applications just as they buy many forms of desktop software today.

"Beyond the protection of the environment itself, people are already going a step further; they already know that they need to protect bits that make up the data now that some of the most valuable data a company can have is on the hips of c-level executives around the globe," said Paul Miller, managing director for Mobile Security at Cupertino, Calif.-based Symantec.

Experts admit that few mobile viruses have plagued smartphone users yet despite the known existence of a sizeable number of proof-of-concept attacks, but some predict that handheld malware is coming.

Miller said that Symantec is convinced that there will even be widespread attacks that spy on not only data, but also phone conversations. So-called snoopware applications, used to listen-in on audio input received by a device's microphone, are very real and may be used in targeted ways to listen-in on specific individuals, he said.

On the same day, Symantec's closest rival, Santa Clara, Calif.-based McAfee, announced a new program to inspect and certify mobile content and applications for network operators and other wireless carriers. The idea is to keep unapproved software from finding its way onto the operators' networks.