Are your handheld mobile devices sitting ducks? In the first three months of 2006, more than 22 different mobile viruses had already been identified by antivirus software provider Symantec.

And that's not the only threat. Because of their small size, handheld devices are easily lost or stolen. Many handhelds come with password protection. Experts say, however, that hackers can easily bypass the password log-in and access any sensitive information contained in the device.

Also, most devices don't have specific access rules. "Once the password has been entered, access has been granted to every part of the device," says Jonathan Read, a spokesman for the Mobile Antivirus Researchers Association, a non-profit group that helps prevent the spread of malicious code.

Mobile devices include some security provisions, but third-party software options can help information-technology managers secure their devices more effectively. Antivirus software for mobile devices is designed to scan for and block malicious code; vendors include McAfee, Symantec and F-Secure.

Another class of software—from Bluefire Security Technologies, Credant Technologies and others—provides encryption, authentication and security management tools. The management software creates a firewall on the device, and even alerts the user to a violation.

Mobile security management software helps protect against workers' bad habits as well. Says Paul Miller, director of mobile and wireless for Symantec: "Employees with smart phones will open attachments from people they don't know, which they would never do with a desktop, and accidentally transfer a virus into the corporate network."

To see the details behind this mobile security calculator and fill in your own estimates, click on the "Get the Tool" icon above to download the interactive worksheet.